Ecology and Ecosystems Ecosystems in the Open Sea

Ecology and Ecosystems Ecosystems in the Open Sea
Choose to view chapter section with a click on the section heading. Ecology and Ecosystems Ecosystems in the Open Sea Coastal Ecosystems - Estuaries, Salt Marshes, Mangrove Swamps, Seagrasses Coastal Ecosystems - Intertidal Zones, Beaches, Kelp and Seaweed, Coral Reefs Polar Ecosystems Deep-Sea Ecosystems Chapter Topic Menu

Ecology and Ecosystems
Chapter 16 Pages 16-3 to 16-9

The Science of Ecology With the rise of environmental awareness, the term ecology has become a buzzword thrown about by the media and politicians. You may already have a general idea of what ecology is, but to discuss marine ecology clearly it’s important to be precise and specific. Ecology and Ecosystems Chapter 16 Page 16-3

The Science of Ecology Ecology is the science that studies how organisms relate to each other and their environment. Ecology embraces the broad range of disciplines, including biology, physics, geology, climatology, oceanography, paleontology, and even astronomy. Beyond biotic (living) factors, the study of ecology considers the abiotic (nonliving) aspects of the environment. Ecology and Ecosystems Chapter 16 Page 16-3

The Science of Ecology Abiotic aspects include temperature, wind, pH, currents, minerals, and sunlight. Ecology also examines the biological factors, such as the quantity and type of organisms in an environment. Ecology studies the relationships and interactions of the abiotic and biotic aspects of the environment. The goal is to understand how, through relationships and interactions, changes in an environment will affect those organisms in the environment. In marine ecology, the four branches of oceanography come together. Ecology and Ecosystems Chapter 16 Page 16-3

Ecology Terminology At some level you’re probably familiar with the concept of an ecosystem. Definition: A distinct entity usually with clearly defined physical boundaries, distinct abiotic conditions, an energy source, and a community of interacting organisms through which energy is transferred. No ecosystem exists entirely in isolation (except under artificial conditions). The ocean is composed of interacting, complex ecosystems. Ecology and Ecosystems Chapter 16 Pages to 16-5

Ecology Terminology A community is a collection of different organisms living and interacting in an ecosystem. This includes all species and types of organisms. A population is a group of the same species living and interacting within a community. The interaction is part of the definition because sometimes two populations of the same species live in a single community. Can you think of examples? Ecology and Ecosystems Chapter 16 Pages to 16-5

Ecology Terminology A habitat includes the area and conditions in which you find an organism. Some species are adapted to or occur in very specific habitats, whereas others range over a variety of habitats. Chitons, for example, live in the rocky intertidal zone, whereas octopuses live in a wide depth range and in many different parts of a reef. The chiton has a narrowly defined habitat compared to the octopus. Ecology and Ecosystems Chapter 16 Pages to 16-5

Ecology Terminology A microhabitat exists on a very small scale. For example, tiny crustaceans and worms live in the spaces between sand grains on the sea floor. Organisms in this microhabitat are a type of infauna called meiofauna. Ecology and Ecosystems Chapter 16 Pages to 16-5

Ecology Terminology An organism’s role in its habitat is called its niche. Very different species can occupy the same niche. On coral reefs, for example, cleaner-shrimp and cleaner-fish both survive by feeding on the parasites and dead or injured skin of reef fish. To avoid confusing habitat and niche, think of the habitat is an organism’s address, and the niche as it’s job. Ecology and Ecosystems Chapter 16 Pages to 16-5

Energy Flow and Nutrient Cycles
Trophic relationships and nutrient cycles are concepts fundamental to ecology. They describe how energy and matter form the basis for interaction among organisms and between organisms and the environment. Recall that photosynthesizers and chemosynthesizers bring energy from the sun and chemicals into the food web. This energy transfers up through the food web, but most of the energy gets lost as heat in the process. Only about 10% of the available energy passes from one trophic level to the next. Ecology and Ecosystems Chapter 16 Pages to 16-8

This illustration shows how energy flows through a functioning ecosystem. Ecology and Ecosystems Chapter 16 Pages to 16-8

The energy flow through the food web affects an ecosystem by determining how much energy is available for organisms at higher trophic levels. In all ecosystems, there are fewer high-level predators than low-level prey. The amount of primary production shapes the ecosystem. High primary production creates the potential for more organisms at high trophic levels, and the potential for more trophic levels. Anything that affects energy flow will also affect the ecosystem. Even with ample primary production the ecosystem would lose many of the high-level organisms in its community. Ecology and Ecosystems Chapter 16 Pages to 16-8

Interrupted energy flow. A substantial decline in an ecosystem’s primary consumers disrupts energy flow to higher trophic levels. Here we see a reduction of the amount and types of prey available to killer whales. The whale population will suffer in this ecosystem unless they move on to an area with more productivity, or more primary consumers to transfer energy to higher trophic levels. Ecology and Ecosystems Chapter 16 Pages to 16-8

Energy flows through an ecosystem, eventually being lost as heat into the water, atmosphere, and space. Nutrients, on the other hand, aren’t lost. Carbon, nitrogen, phosphorus, and other crucial elements cycle through the Earth’s ecosystems. Ecology and Ecosystems Chapter 16 Pages to 16-8

The nitrogen nutrient cycle is thought to be more limited in marine ecosystems than in terrestrial ecosystems. Because: Inorganic nitrogen must be fixed into organic compounds before it can be used by organisms. Nitrogen-fixing bacteria that do this live primarily in terrestrial ecosystems. Seabird droppings, erosion, and runoff carry organic nitrogen compounds (and phosphorus) from terrestrial environments into the marine environment. This is an example of how ecosystems don’t exist entirely in isolation. Ecology and Ecosystems Chapter 16 Pages to 16-8

Nitrogen Cycling Ecology and Ecosystems Chapter 16 Pages to 16-8

The ecological significance of nutrient cycles is usually greater than that of energy flow. Why? Nutrients are usually a limiting factor, whereas energy is usually not. Compare many warm, tropical marine ecosystems with cold, temperate marine ecosystems. Tropical ecosystems generally have more energy (sunlight) available, yet oceanic conditions don’t supply as many nutrients to tropical regions. One of the few highly productive marine ecosystems found in tropical waters is the coral reef. Temperate coastal waters, by comparison, have less overall sunlight, but receive far more nutrients. For this reason, the most highly productive marine ecosystems are found in colder water. Ecology and Ecosystems Chapter 16 Pages to 16-8

Ecosystems in the Open Sea
Chapter 16 Pages to 16-14

Euphotic Zone Ecosystems
The euphotic zone comprises only 1% of the ocean, yet the majority of marine life lives there. Extends as deep as 200 meters (656 feet), but in coastal waters with more turbidity, light may only penetrate to about 30 meters (100 feet). The euphotic zone is where photosynthetic organisms live, and light energy transfers through food webs as chemical energy. Ecosystems in the Open Sea Chapter 16 Pages to 16-12

The neuston are the plankton that live in the uppermost layer of the ocean. This ecosystem is very thin – only a few millimeters in many instances. It receives the maximum sunlight and because it covers about 71% of the Earth’s surface. Ecosystems in the Open Sea Chapter 16 Pages to 16-12

There have been surprisingly few studies to compare the neuston layers to the water layers below. It is known that the first few millimeters to a few centimeters of water differ substantially from the water below. Generally, neuston layers hold significantly more nutrients, chlorophyll a, and carbon compounds. Surface tension supports eggs, larvae, and microscopic life on the top film of the water. Cyanophyte, diatom, and dinoflagellate populations in the neuston ecosystem may be 10,000 times more numerous than in the water just a few millimeters deeper. This makes the neuston zone an important ecosystem for worldwide primary productivity. Ecosystems in the Open Sea Chapter 16 Pages to 16-12

This isn’t true globally, however. In some places, photosynthesis and primary productivity are higher below the neuston ecosystem. One reason may be photoinhibition. Photoinhibition seems to be prevalent in tropical seas. Because there’s little water to protect neuston organisms, ultraviolet light may account for some of the photoinhibition. If this is true, ozone depletion may make photoinhibition worse as even more UV light makes it to the Earth’s surface. Ecosystems in the Open Sea Chapter 16 Pages to 16-12

An important factor reducing primary productivity in the neuston ecosystem may be pollutants. A variety of pollutants from the atmosphere and runoff enter the euphotic zone. How pollutants affect the neuston ecosystems concerns scientists with respect to global climate change. The ocean plays an important role in moderating global climate - particularly removing CO2. Many oil-based chemicals, float on water, creating a barrier that slows or stops carbon dioxide (and other gases) from dissolving into the water below. By affecting the euphotic zone ecosystems, these pollutants may contribute to global climate change. Ecosystems in the Open Sea Chapter 16 Pages to 16-12

Floating debris, whether natural or human-produced, acts as potential shelter and attracts marine life. This creates distinct neustonic ecosystems that thrive around floating material in the water. The world’s largest floating ecosystem is the Sargasso Sea - a complex community. Sargassum mat organisms include tiny fish of many species, crustaceans, and other organisms. On the other hand, the Sargassum fish is a species of frogfish adapted specifically to this ecosystem. It blends in with the Sargassum, preying on small crustaceans and fish. Ecosystems in the Open Sea Chapter 16 Pages to 16-12

The Sargasso Sea and other euphotic zone ecosystems found around floating debris provide another example of how ecosystems interact. Predatory fish hide under Sargassum or debris, feeding on fish and other neustonic organisms that live there. These predators in turn provide food for pelagic fish, sharks, dolphins, and other large predators. Ecosystems in the Open Sea Chapter 16 Pages to 16-12

Continental Shelf Ecosystems
The neritic zone consists of the water between the low-tide mark and the edge of the continental shelf. This zone can range from only a few to several hundred kilometers or miles wide. The neritic zone is a significant marine ecosystem because it is the most productive region in the ocean. The area tends to keep nutrients in the shallow, photic zone and helps retain heat from the sun. Being near the shoreline - the neritic zone benefits from nutrients in river runoff also. Nutrients rising with currents from deep water at the shelf edges also make this zone biologically rich. All of these factors combine to make the neritic zone a highly productive ecosystem. Ecosystems in the Open Sea Chapter 16 Pages to 16-14

Ecosystems in the Open Sea Chapter 16 Pages to 16-14 Neritic Zone Productivity

Upwelling plays a significant role in the balance of coastal ocean ecosystems. This is because upwelling brings nutrients from deeper water to shallow, more productive depths. This is especially significant with respect to fecal pellets and other nutrients that sink to the relatively less productive bottom in the abyssal zone. Wind causes upwelling that returns nutrients to the upper ocean depths. Ecosystems in the Open Sea Chapter 16 Pages to 16-14

The role of upwelling is unmistakable. Areas with the highest upwelling activity also have the highest nutrient levels. These correspond with many of the ocean’s highest productivity regions. Examples include the waters offshore of Peru, the Bering Sea, the Grand Banks in the Atlantic, and the deep water surrounding Antarctica. Ecosystems in the Open Sea Chapter 16 Pages to 16-14

Ecosystems in the Open Sea Chapter 16 Pages to 16-14 Areas of Coastal Upwelling

Coastal Ecosystems - Estuaries, Salt Marshes, Mangrove Swamps, Seagrasses
Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-22

High Productivity Marine Environments
Coastal ecosystems are generally highly productive ecosystems for several reasons. They benefit from nutrient-rich runoff from land. Because they’re shallow, the benthic organisms in these ecosystems live in the upper photic zone, instead of the bottom as in the open sea. Salt-tolerant plants can grow in the well-lit shallows, providing shelter. These plants act as the foundation for several different types of ecosystems that cannot exist in the open ocean. Coastal Ecosystems - Part 1 Chapter 16 Pages 16-15

The combination of nutrients, ample light, and shelter make coastal ecosystems diverse and rich. While you don’t commonly find large organisms here (though there are some), these ecosystems provide a haven for juveniles of open ocean species. Mangrove swamps contribute to the health of coral reefs in this way. Coastal Ecosystems - Part 1 Chapter 16 Pages 16-15

Human activities have wide-ranging potential effects on coastal ecosystems. The effects are varied and immediately at hand. People have always tended to live near water, putting humans in proximity with these ecosystems - this causes problems. Agriculture, for example, can alter these ecosystems when excess fertilizer washes seaward with rain runoff. Can you name more? The variety of human activities is so wide we can’t always anticipate all the consequences to ecosystems. Coastal Ecosystems - Part 1 Chapter 16 Pages 16-15

Because the effects are immediately at hand, coastal ecosystems may experience the consequences more severely. Pollutants, for example, often reach coastal ecosystems in concentrated form. Open ocean ecosystems, by contrast, benefit from a diluting effect. Coastal Ecosystems - Part 1 Chapter 16 Pages 16-15

One particular concern with coastal ecosystems is eutrophication, which is an overabundance of nutrients that causes an ecological imbalance. Eutrophication is a stimulus to some species and a detriment to others. Fertilizer runoff can dump excess nutrients in the water, stimulating excessive algae growth or algae blooms. When the algae die, degradation of biomass consumes available oxygen. The depletion of oxygen kills fish and other sea life. Although there are other causes of harmful algae blooms (HABs), eutrophication is the most conspicuous. Coastal Ecosystems - Part 1 Chapter 16 Pages 16-15

Estuaries Estuaries exist where the tides meet rivers.
They’re not found where all rivers enter the sea, but they’re common where the tidal range is high. This allows high tide to push well up river, often flooding large land areas. Estuaries may be large, complex deltas with multiple inlets, lagoons, and islets or they may be simple wide stretches of river entering the sea. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-17

Estuaries Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-17

Estuaries Estuaries tend to trap and accumulate runoff sediments, so they’re rich with nutrients and biologically productive. Most of the major North American rivers flowing into the Atlantic flow first into estuaries. This is why the North Atlantic doesn’t have as much sediment flowing in to it as other ocean basins have with comparable rivers. Estuaries trap much of the sediment. This also makes estuaries sensitive to eutrophication because the same process traps excess nutrients such as fertilizer runoff. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-17

Estuaries Estuaries act as a dumping ground, filter, and absorber of nutrients (and pollutants). Estuaries are the kidneys of the biosphere because of their cleansing function. The continuous replenishment of nutrients results in ecosystems with high primary productivity from algae and halophytes - saltwater plants. These, in turn, support a large community of primary and secondary consumers. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-17

Estuaries Some factors limit productivity in estuaries.
One is that organisms in this ecosystem must tolerate wide salinity ranges. The osmotic stress caused by the rising and falling tides mixing with fresh water proves fatal to many organisms. Organisms that tolerate wide salinity ranges are called euryhaline organisms. Therefore, variations in salinity tend to reduce the variety of species. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-17

Estuaries Another productivity limit results from the tendency of decomposition to deplete the oxygen in the nutrient-rich sediments. This limits the benthic organisms that can thrive in estuaries. The rotten eggs smell common to these areas comes from sulfides released by thriving anaerobic sulfur bacteria. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-17

Estuaries Estuaries provide a region of shallow, sheltered water and nutrients, making them excellent nurseries. By providing a rich haven, larvae and juveniles of open ocean species can elude predation and grow before venturing out to sea. Estimates show that estuary ecosystems serve as nurseries for more than 75% of commercial fish species. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-17

Estuaries Estuaries contribute to the productivity of adjacent marine ecosystems in at least two ways. First, surviving juveniles migrate from the estuaries as they grow and mature. They increase the number of individuals that survive the hazardous larval and juvenile stages. Second, estuaries provide a steady stream of nutrients to adjacent marine ecosystems, while trapping sediment and other materials in runoff from rain and storms. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-17

Salt Marshes Salt marshes exist in estuaries and along the coasts.
They are found where flat, gently sloping shore are washed by the tides with nutrient-rich sediments. Rivers provide a source of sediments and nutrition. Conditions within a salt marsh vary, which affects the types of organisms inhabiting different areas within the ecosystem. The upper marsh includes the areas only rarely flooded by the tides. The lower marsh includes areas flooded by salt water as a regular part of the tidal cycle. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-19

Salt Marshes Salt Marsh Plant Community Coastal Ecosystems - Part 1

Salt Marshes Most plants can’t live in seawater because osmosis dehydrates them. Halophytes, on the other hand, have adaptations that allow them to survive in salt water. Thanks to these adaptations, halophytes occupy a niche with little competition from other plants, and become the dominant species. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-19

Salt Marshes Halophytes in the lower marsh deal with constant osmotic stress. The hollow reed Spartina sp., called cordgrass, is a good example of halophyte adaptation to this part of the ecosystem. Spartina sp. excludes salt from its tissues and moves oxygen it produces by photosynthesis to its roots. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-19

Salt Marshes Plants in the upper marsh don’t have to deal with daily tides. In addition, the inflow of fresh water dilutes salt water, reducing osmotic stress. Organisms thriving in this part of the ecosystem adapt differently. One example is Salicornia sp., or pickleweed. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-19

Salt Marshes Pickleweed handles excess salt by storing it in sacrificial leaves. When the salt load accumulates to a certain point, the leaf drops away, taking the salt with it. Salicornia grows another leaf to take its place. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-19

Salt Marshes Halophytes dominate the salt marsh, yet they are not food for many organisms. Salt marsh plants are tough and salty, making them unsuitable for most herbivores. Their root systems hold sediment, which, along with the accumulation of dead halophytes, creates dense mats of detritus. In the salt marsh, detrital mats provide habitats for huge communities of invertebrates, water birds, juvenile fish, larva, eggs, and other organisms. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-19

Salt Marshes Food Web Coastal Ecosystems - Part 1
Chapter 16 Pages to 16-19 Food Web

Mangrove Swamps Mangrove swamps include many species.
They all play an important role in the marine environment, especially coral reefs. In many respects, mangroves occupy similar niches as the halophytes that characterize salt marshes, but they’re bigger, tougher, and found in tropical climates. Mangrove species have various adaptations that allow them to live in salt water and anaerobic mud. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-21

Mangrove Swamps Red mangroves grow above the waterline on stilt-like roots. This allows oxygen to reach the roots. a. They obtain fresh water by filtering seawater through its adapted roots, which exclude the salt. This is an example of reverse osmosis, which is the process of transporting water through a semipermeable membrane against the natural osmotic pressure gradient. This is a form of active transport, which is the process of a cell moving materials from areas of low concentration to areas of high concentration. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-21

Mangrove Swamps Black Mangroves have roots that grow in the sediment below the waterline. These mangroves aerate their roots with snorkel-like tubes called pneumatophores, which carry air from above the surface to the roots. Some black mangroves eliminate salt through sacrificial leaves, like the pickleweed. Others have special salt glands in their leaves. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-21

Mangrove Swamps White mangroves lack such specialized adaptations.
They’re very saltwater tolerant, but thrive high on the tideline where they don’t need special root adaptations. These mangroves receive sufficient freshwater runoff to survive. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-21

Mangrove Swamps Regardless of species or adaptations, mangroves share two important characteristics that make them the basis of mangrove ecosystems. They have strong, tangled roots that provide habitats for juvenile fish and invertebrates - they are nurseries for nearby marine ecosystems, particularly coral reefs. They hold the soil well, protecting the habitat and coast from erosion due to storm surges, waves, and weather. Without strong mangrove root systems, tropical storms would quickly wash away many tropical islands and beaches. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-21

Mangrove Swamps Mangroves trap nutrients, much as estuaries do, helping to protect coral reefs and other nearby marine ecosystems. However, because they’re swampy, sulfide-smelling mosquito havens, until relatively recently people viewed them as wastelands. Today we know they’re ecosystems crucial to the global ecosystem, but mangroves continue to vanish. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-21

Seagrasses Seagrass ecosystems are similar to other halophyte-based ecosystems in that they stabilize sediments and provide shelter and habitats for other organisms. However, seagrasses differ from other halophytes in several important ways that make them and their ecosystems distinct. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-22

Seagrasses Seagrasses are rooted, vascular flowering plants that live entirely under water except during rare, very low tides. Some species live as deep as 30 meters (100 feet). Seagrasses can grow as members of a mangrove or salt marsh ecosystem. Commonly seagrass grow spread across the bottom like underwater pastures - they mat the sediment below. Seagrasses extract oxygen from the water and have internal air canals. Most species even release pollen into the current to reproduce, much like terrestrial plants. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-22

Seagrasses Unlike most halophytes, seagrasses are edible and provide food for ecosystem inhabitants. They are heavily grazed by microbes, invertebrates, fish, turtles, and even manatees and dugongs. Coastal Ecosystems - Part 1 Chapter 16 Pages to 16-22

Coastal Ecosystems - Intertidal Zones, Beaches, Kelp and Seaweed, Coral Reefs
Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-29

Intertidal Zones When we think of coastal ecosystems, we tend to think of mangroves, estuaries, and similar ecosystems. The numerous complex organisms make their productivity conspicuous. However, in every place the ocean touches land, you’ll find a coastal ecosystem with rich communities. Ecosystems in the world’s intertidal zones exist in areas that may be above the waterline at times. Other portions of intertidal zones reach depths of about 10 meters (33 feet). Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-24

Intertidal Zones The supralittoral zone is the area only submerged during the highest tides. The greatest challenges facing organisms that live in supralittoral ecosystems are drying and thermal stress. A constant spray of seawater that evaporates also results in high salt levels. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-24

Intertidal Zones Organisms with habitats in the supralittoral zone have adaptations that help them retain moisture. Unlike many marine organisms, they can either obtain oxygen from the air or store sufficient oxygen in their tissues to endure many hours out of the water. They are hardy enough to withstand periodic motion and pounding by waves. Barnacles, periwinkles, and limpets are examples of organisms adapted to life in the supralitttoral zone. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-24

Intertidal Zones The rest of the littoral zone (the area between high and low tide) faces similar challenges. Life here isn’t left above the surface for extended periods like the supralittoral zone. These organisms also face the challenges of drying out, thermal stress, and water motion. Progressing seaward, the environment becomes less stressful with respect to drying out and thermal stress, though waves and surge remain challenges. Organisms that thrive here are seaweeds, starfish anemones, and mussels. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-24

Intertidal Zones The lowest part of the littoral zone is rarely exposed to air - only at extremely low tides. With ample water, nutrients, and sunlight, this is a highly productive region in most coastal ecosystems. One challenge to life here, therefore, is intense competition. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-24

Intertidal Zones Rocky Shore Community Coastal Ecosystems - Part 2

Beaches To the untrained eye, the typical sandy beach appears nearly devoid of life. It looks almost like a desert, with only an occasional shell or starfish. The reality is that beaches are rich and productive ecosystems. They also have important roles that affect other marine ecosystems. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-25

Beaches Sand results from the energy of waves weathering the coast and washing it into the sea with river runoff. Scientists think that the sands on the world’s beaches may have migrated thousands of years before washing ashore. In addition to minerals, living and dead organic material accumulates into the sand mix. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-25

Beaches Sand protects the coastline.
As a wave comes ashore, it picks up sand. Each sand grain dissipates a miniscule portion of wave energy. That portion times billions and billions of sand grains reduces the forces that wear away the coastline. This is the first way that beaches affect ecosystems. They reduce sedimentation caused by coastal erosion. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-25

Beaches Beach ecosystems are rich in organisms living on the organic material in the sand mix. Complex organisms, including worms, mollusks, and fish live in the submerged beach sand. Called meiofauna - benthic organisms that live in the spaces between sand grains are very diverse. About a third of all known animal phyla have representatives in the meiofauna. Additionally, algae and other non-animal organisms live among the sand grains. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-25

Beaches The interaction between water motion and the meiofauna provides the second way that beaches affect other marine ecosystems. The physical and organic processes in the beach ecosystem break down organic and inorganic materials. This makes the beach a giant filter that processes compounds from runoff to the sea or washed up from the sea. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-25

Kelp and Seaweed Ecosystems
Seaweed refers to a diverse group of red, green, and brown algae. All provide the bases for ecosystems among their stipes, holdfasts, and blades. Among these, kelp ecosystems are probably the most diverse. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-27

You find kelp forests globally in cool water. This is because they require the nutrients found in a cool ocean. The richest and most productive kelp ecosystems exist in coastal waters with upwellings. In clear water with ample sunlight and nutrients, giant kelp can reach 60 meters (196.8 feet) long that cover many acres underwater. Kelp forests and other seaweed-based ecosystems are among the most biologically productive ecosystems. Their primary production exceeds the primary productivity of terrestrial forests and is almost equal to the productivity of coral reefs. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-27

Because of its dependence on sunlight, cool water, and nutrients, kelp responds noticeably to environmental changes. During ENSO events, for example, the coastal water temperatures in Southern California rise. This often causes massive die offs of kelp, disrupting the local ecosystems for a year or more. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-27

Kelp provides a clear example of why it’s important to study ecology, not simply individual organisms. Until protected, in some areas the sea otter was hunted nearly to extinction. Amazingly, in these areas the kelp began to die off rapidly. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-27

It turns out that while few organisms eat kelp, one that does is the sea urchin. These echinoderms graze on the rubbery holdfasts that anchor the kelp. Sea urchins are also one of the sea otter’s primary foods. The energy required by a mammal living in cool seawater is considerable, so the average sea otter eats a substantial number of sea urchins. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-27

Killing the sea otters disrupted the kelp forest’s ecological balance by removing the sea urchin’s chief predator. This allowed the sea urchin population to rise relatively unchecked. More sea urchins meant more grazing on kelp holdfasts. In the end, the sea urchins ate the kelp faster than it could grow. This is an excellent example of the interdependence that exists within an ecosystem. It shows that each organism contributes to a balance that allows life to thrive there. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-27

Coral Reefs Of all the Earth’s ecosystems, few compare to the coral reef. Most scientists believe they are the most taxonomically diverse ecosystems in the ocean. The Indo-West Pacific area between Papua New Guinea and the Sulu and Celebes Seas has the world’s highest marine species diversity. More than 2,000 species of fish are known, with new species discovered every year. Scientists think corals and coral reefs originated here because the further you go from this area, the less diversity you find. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-29

Coral Reefs Coastal Ecosystems - Part 2

Coral Reefs While supporting immense diversity, coral reef ecosystems are also fragile. For decades now, scientists, divers, and others familiar with coral have been worried about their health. The conditions coral requires for life are narrow and specific. It lives in clear water so that dinoflagellates (zooxanthellae) coexisting in the polyps have light for photosynthesis. It also needs water that’s in moderate motion to prevent sediments from accumulating on the polyps. Particulate matter can clog and smother the polyps. It also reduces the light reaching the algae inside. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-29

Coral Reefs Coral ecosystems also require water that’s relatively free of nutrients. This may seem odd considering the high productivity of this ecosystem. However, coral ecosystems efficiently pass on and preserve organic material. The lack of nutrients in the water actually protects coral from competitive organisms. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-29

Coral Reefs This is why eutrophication is one of the biggest threats to coral ecosystems. A rise in water nutrient levels allows competitive algae to overgrow and smother coral colonies. It also allows plankton to grow, reducing water clarity and the amount of sunlight reaching the polyps. To some extent, these are natural processes, but over the last several decades eutrophication levels have been rising. Correspondingly, many reefs once dominated by corals now have algae overgrowing them. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-29

Coral Reefs Besides eutrophication, thermal stress threatens coral reef ecosystems. A concern is that global warming may raise temperatures above coral’s survival threshold. Another threat comes from sedimentation resulting from coastal dredging and construction. This causes sediment to accumulate on the polyps more quickly than water motion can remove it. Coral diseases seem to be more common. These are “attacks” by fungi, cyanophytes, bacteria, and other competitive algae damaging and displacing corals. Scientists are still determining the likely sources and causes for many of these. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-29

Coral Reefs Regardless of the specific threat, it’s important to apply the principles of ecology to the overall picture. The concern isn’t for the coral alone, but the entire coral ecosystem. Just as the loss of sea otters threatens kelp, the loss of the corals threatens other organisms in the ecosystem. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-29

Coral Reefs Parrotfish, for example, feed on coral. If the coral dies, the parrotfish will dwindle as they lose their primary food source. Predators that feed on the parrotfish may similarly suffer. Other organisms will not survive because the competitive algae don’t provide the same habitat as a coral reef. The decline of coral is likely to have a domino effect throughout not just the coral ecosystem but the entire marine ecosystem. Ultimately, that means the loss of coral will affect the global ecosystem in ways that ecologists are still trying to predict. Coastal Ecosystems - Part 2 Chapter 16 Pages to 16-29

Polar Ecosystems Polar Ecosystems Chapter 16 Pages to 16-32

The Arctic The Arctic Ocean is bordered by the shallow continental shelves of North America, Greenland, Eurasia and Russia. It connects to the rest of the ocean at the Bering Straight and the upper North Atlantic. The Arctic is a deep basin and much of this sea is a permanently frozen ice cap. Polar Ecosystems Chapter 16 Pages to 16-31

The Arctic Marine ecosystems in the Arctic face the challenges of reduced sunlight under the ice and water that’s barely above freezing. For these reasons, divesity of organisms is limited under the permanent ice cap. Species that do live in these conditions have special adaptations. These include antifreezing compounds in their blood and extremely low metabolisms. Polar Ecosystems Chapter 16 Pages to 16-31

The Arctic At the edge of the ice cap, however, life intensifies especially between March and September. As the sun melts ice in the spring, water flows off the ice, sinking into deep water. Warm currents from the south interact with the cold water at the continental shelf edges. This process churns up nutrients from the shelf bottom. Polar Ecosystems Chapter 16 Pages to 16-31

The Arctic Extremely high productivity occurs along an arc in the North Pacific and across the North Atlantic from April to August. These waters support massive fisheries, marine mammals, and other organisms. This ecosystem flourishes from the nutrients churned up from the bottom. Polar Ecosystems Chapter 16 Pages to 16-31

The Antarctic Antarctica has a more extreme climate than the Arctic.
Also, the Antarctic differs geographically from the Arctic. Antarctica, is a continent, not a frozen sea. Polar Ecosystems Chapter 16 Pages to 16-32

The Antarctic It’s also not enclosed by the continental shelves of other continents. Instead, it has its own continental shelf. The deepest and broadest ocean ring surrounds the Antarctic. For these reasons, the Antarctic ecosystem has differences and similarities compared to the Arctic. Polar Ecosystems Chapter 16 Pages to 16-32

The Antarctic During the winter, sea ice surrounding Antarctica freezes, adding an area about the size of North America. When summer comes, the melting of this sheet sets off an explosion of bioproductivity. As the temperature of the seawater drops, water molecules join together to form sea ice. When the ice forms, the salts become concentrated in the remaining seawater. This very cold, very salty, very dense water flows down the continental margins of Antarctica and becomes Antarctic Bottom Water, the most dense water in the ocean. Winds blowing along the coast result in Ekman Transport, which moves water away from the continent at the surface, causing upwelling in the area. Polar Ecosystems Chapter 16 Pages to 16-32

The Antarctic This nutrient-rich deep water reaches the surface at the Antarctic Divergence, an area located at approximately 65˚ to 70˚ south latitude. This is the largest nutrient-rich area on Earth. The Antarctic Divergence supports massive phytoplankton blooms from November through the southern summer. The copepod and krill populations are larger than any other species population found in any other ecosystem. Single krill swarms have been estimated as exceeding 100 million tons, which is more than the world’s annual commercial fish catch. Polar Ecosystems Chapter 16 Pages to 16-32

The Antarctic The productive water zone extends northward until it meets the warm Atlantic, Indian, and Pacific waters. At this point, the cold Antarctic water sinks under the warm water. This area is called the Antarctic Convergence. It is located at approximately 50˚ to 60˚ south latitude. As in the Arctic, organisms living in the coldest Antarctic ecosystems have special adaptations. Because the Antarctic is a relatively isolated ecosystem, most species are specialized and found only in the Antarctic. Polar Ecosystems Chapter 16 Pages to 16-32

Deep-Sea Ecosystems Deep-Sea Ecosystems

The Abyssal Zone In the deep ocean beyond the continental shelves, the sun’s light and warmth never reach the bottom and the average temperature is 2˚C (35.6˚F). Without sunlight, there’s no photosynthesis; consequently, there’s no primary productivity in most of the deep ocean. Deep-Sea Ecosystems Chapter 16 Pages to 16-34 Viperfish

The Abyssal Zone Because there’s no primary productivity, most of the deep ocean gets its nutrients from marine snow. Marine snow is the constant fall of sediment, dead organisms, fecal pellets, and other nutrients from the productive shallow waters above. Most of the deep ocean is the abyssal zone, which covers about 30% of the Earth’s surface. This is one of the smoothest and flattest areas on Earth, found at depths between about 3,000 and 4,000 meters (9,843 and 13,123 feet). Without primary productivity, the abyssal zone lacks dense life concentrations. However, there’s a vast species diversity. Deep-Sea Ecosystems Chapter 16 Pages to 16-34

The Abyssal Zone Marine snow makes the deep ocean rich in nutrients. However, the nutrients are spread out evenly. Without photosynthesis, there’s insufficient energy accumulated to support a great abundance of multicellular organisms. Those that do survive are primarily echinoderms, such as sea cucumbers, sea lilies, and brittle stars. Concentrations of large organisms are rare. However, submersibles have seen rattails, deep-sea dogfishes, catsharks, crustaceans, mollusks, and many species of deep ocean fish. Deep-Sea Ecosystems Chapter 16 Pages to 16-34

The Abyssal Zone The greatest diversity in the abyssal zone is found in the meiofauna. As in beach sand, you can find representatives from almost all the animal phyla living in the deep ocean mud or sediment. The concentrations and populations are lower than in shallower seas, but the diversity is not. Scientists have explored only a small portion of the abyssal zone. It is not unusual for new species to be found there. It is one of the last frontiers on Earth to be explored. Deep-Sea Ecosystems Chapter 16 Pages to 16-34

Whale Falls Although the abyssal plains are typical of most of the deep-ocean ecosystems, there are some important exceptions, including whale falls. A whale fall is exactly what the name says - a place where a dead whale comes to rest on the deep ocean floor. Deep-Sea Ecosystems Chapter 16 Pages to 16-35

Whale Falls Whale carcasses provide a massive concentration of nutrients in areas that normally only receive diffuse marine snow. Scientists think that the result is the development of a distinct local ecosystem that goes through three distinct stages. The first stage is when the scavengers arrive. They consume the whale’s soft tissues in a few months. Hagfish, grenadiers, deep-sea spider crabs, and sleeper sharks are some of the scavengers associated with this stage. Deep-Sea Ecosystems Chapter 16 Pages to 16-35

Whale Falls The second stage lasts about a year.
Worms, small crustaceans, and other small organisms feed on the remaining soft tissue and the tissue dispersed around the whale as detritus. Marine biologists are still trying to determine exactly how these organisms find their way to the whale. The current thinking is that the larval stages for these animals is widely dispersed, and settle on food when it becomes available to complete development. Deep-Sea Ecosystems Chapter 16 Pages to 16-35

Whale Falls The final stage involves the decay of the whale skeleton.
This can last several years or even decades. The bones provide a steady supply of sulfide as they’re broken down. Chemosynthetic bacteria live on this sulfide, creating a food source for tubeworms, crustaceans, gastropods, and bivalves. These bacteria appear to be the same as those associated with hydrothermal vents. It may be that whale falls enable the colonization of these deep-sea ecosystems. Deep-Sea Ecosystems Chapter 16 Pages to 16-35

Whale Falls If this is the case, the effects of whaling on these deep ecosystems may be substantial. Other large organisms sinking to the deep ocean bottom have a similar effect. Wood, kelp, Sargassum, and large fish provide a nutrient concentration that supports a local ecosystem for several months to a year. Deep-Sea Ecosystems Chapter 16 Pages to 16-35

Hydrothermal Vents and Cold Seeps
Hydrothermal vents are sources of primary productivity. Around these vents, chemosynthesizing bacteria consume sulfides dissolved in the heated water emerging from these vents. These bacteria act as the base of a trophic pyramid for a diverse community living in these deep ocean ecosystems. Deep-Sea Ecosystems Chapter 16 Pages to 16-36

Similar to hydrothermal vents, cold seeps are areas where hydrocarbons and sulfide-rich fluids seep from the underlying rock in the ocean floor. These are called “cold” seeps because they’re cool compared to hydrothermal vents. However, they are heated by geothermal energy from inside the Earth. Deep-Sea Ecosystems Chapter 16 Pages to 16-36

Like the hydrothermal vents, cold seeps support chemosynthetic-based ecosystems. The chemosythesizers include the same sulfide-consuming bacteria, but other vents and seeps rely on microbes that consume methane or other hydrocarbons. Deep-Sea Ecosystems Chapter 16 Pages to 16-36

The Hadal Depths - Ocean Trenches
The hadal zone makes up the deepest ocean depths, found in the deep ocean trenches where the oceanic plates collide with continental plates. Depths in this zone range from about 5,000 to 6,000 meters (16,400 to 19,700 feet), although some spots are deeper than 11,000 meters (36,000 feet). Deep-Sea Ecosystems Chapter 16 Page 16-36

Scientists know little about the hadal zone ecosystems primarily because of the limits of technology. The extreme pressure makes it expensive and difficult to make submersibles or instruments capable of observing these depths. Only a few submersibles have been built that can descend safely into the hadal zone, and only a single manned trip has been made to the deepest known spot in the ocean. Deep-Sea Ecosystems Chapter 16 Page 16-36

Therefore, what scientists know about life in the hadal zone is limited to fleeting glimpses. Most of these are from ROVs (Remote Operated Vehicles) and brief visits by submersibles. These brief observations have found organisms even in the Mariana Trench (the deepest known place on Earth), but the character and extent of the hadal ecosystems remain largely unknown. Deep-Sea Ecosystems Chapter 16 Page 16-36

Ecology and Ecosystems Ecosystems in the Open Sea

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Ecology and Ecosystems Ecosystems in the Open Sea

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