Presentation is loading. Please wait.

Presentation is loading. Please wait.

Environmental Processes in Oceans and Lakes

Similar presentations

Presentation on theme: "Environmental Processes in Oceans and Lakes"— Presentation transcript:

1 Environmental Processes in Oceans and Lakes
Phytoplankton Dr. Dawn A. Osborn Environmental Processes in Oceans and Lakes

2 About 4000 species of phytoplankton have been described
About 4000 species of phytoplankton have been described. The astonishing diversity with respect to shape, size and color of phytoplankton is visible only under a microscope. One trait all phytoplankton share, however, is chlorophyll—the green pigment that converts energy from the sun into food. (Images copyright Smithsonian Environmental Research). Phytoplankton: freely drifting, photosynthesising microscopic organisms that live in the upper, sunlit layers of the ocean. Phytoplankton are the oceanic equivalents of terrestrial plants, forming the basis of virtually all marine food webs. The total phytoplankton biomass outweighs that of all the marine animals (zooplankton, fish, whales) put together, and phytoplankton productivity is one of the primary forces in regulating our planetary climate - for instance via impacts on atmospheric carbon dioxide levels which are tightly linked to the oceanic concentrations. Autotrophic synthesize their own organic materian from inorganic compounds + primary producers = primary production is the basis of marine production Oxygen Supply Phytoplankton need two things for photosynthesis and thus their survival: energy from the sun and nutrients from the water. Phytoplankton absorb both across their cell walls. In the process of photosynthesis, phytoplankton release oxygen into the water. Half of the world's oxygen is produced via phytoplankton photosynthesis. The other half is produced via photosynthesis on land by trees, shrubs, grasses, and other plants.

3 To see phytoplankton in the coean, one needs to view the ocean from space. Here is a Phytoplankton bloom in the South Atlantic (February 15, 2006). In order to determine the speceis, you would need to collect water samples.

4 Phytoplankton Phyto (Greek, plant) Plankton (Greek, drifter)
Contrast with nekton (Greek, swimmer) fish, whales, big shrimp benthos (bottom dwellers) barnacles, mussels, crabs Macrophytes seaweed In the ocean, most primary production is done by phytoplankton … << 10% is done by seaweed, even less by non-photosynthetic autotrophs. Different habitats for different species Unicellular Microscopic plant in the ocean algae called phytoplankton. Those organisms that drift passively with the current (although still capable of independent movement) are grouped with the plankton. Most (but not all) planktonic organisms are small (greatest diameter under 1 centimeter). Chloroplasts produce energy from light by photosynthesis. Nekton is the grouping of living organisms that live in the water column of the ocean and freshwater lakes. Nekton organisms can propel themselves independent of the currents in the water mass. Some examples are adult krill, small fish, whales, and tuna; the latter two capable of substantial migrations. Nekton lengths range from a few centimeters to 30 meters. One characteristic of nekton is the capability of fast motion. Another is maneuverability, as in linear and angular acceleration, starting, stopping, turning, and in general displaying agility. Macrophytes are the conspicuous plants that dominate wetlands, shallow lakes, and streams. Macrophytes are aquatic plants, growing in or near water that are either emergent, submergent, or floating. Macrophytes are beneficial to lakes because they provide cover for fish and substrate for aquatic invertebrates. They also produce oxygen, which assists with overall lake functioning, and provide food for some fish and other wildlife. The size and speed ranges of plankton and nekton mean that while plankton experience water as a viscous medium, often with reversible flows, the world of nekton is dominated by inertia (sustained vortices, coasting, etc.). Viscosity is a measure of the resistance of a fluid to deform under shear stress. It is commonly perceived as "thickness", or resistance to pouring. Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction. Thus, water is "thin", having a lower viscosity, while vegetable oil is "thick" having a higher viscosity. Oceanic Nekton: There are three types of oceanic nekton: Chordates are the largest and are made up of either bones or cartilage. Molluscans are animals like octupi and squids. Arthrodpods are animals like shrimp. benthos are the organisms and habitats of the sea floor; in freshwater biology they are the organisms and habitats of the bottoms of lakes, rivers, and creeks. Different habitats support different speceis. Diatoms abundant in coastal water, dinoflagellates abundant in all water esp ewarm water. Cyanobacteris and very abundant in the tropics. The lifetime of most oceanic plants pico and nanoplankton is measured in hours or days. Source of Half Earth's Oxygen Gets Little Credit John Roach for National Geographic News June 7, 2004 Fish, whales, dolphins, crabs, seabirds, and just about everything else that makes a living in or off of the oceans owe their existence to phytoplankton, one-celled plants that live at the ocean surface. Phytoplankton are at the base of what scientists refer to as oceanic biological productivity, the ability of a water body to support life such as plants, fish, and wildlife. "A measure of productivity is the net amount of carbon dioxide taken up by phytoplankton," said Jorge Sarmiento, a professor of atmospheric and ocean sciences at Princeton University in New Jersey. The one-celled plants use energy from the sun to convert carbon dioxide and nutrients into complex organic compounds, which form new plant material. This process, known as photosynthesis, is how phytoplankton grow. Herbivorous marine creatures eat the phytoplankton. Carnivores, in turn, eat the herbivores, and so on up the food chain to the top predators like killer whales and sharks. But how does the ocean supply the nutrients that phytoplankton need to survive and to support everything else that makes a living in or off the ocean? Details surrounding that answer are precisely what Sarmiento hopes to learn. Robert Frouin, a research meteorologist with the Scripps Institution of Oceanography in La Jolla, California, said understanding the process by which phytoplankton obtains ocean nutrients is important to understanding the link between the ocean and global climate. "Marine biogeochemical processes both respond to and influence climate," Frouin said. "A change in phytoplankton abundance and species may result from changes in the physical processes controlling the supply of nutrients and sunlight availability."

5 Phytoplankton Marine plants can be motile Advantages??
Spin, rotate, twirl Advantages?? Rise up lighter than sea water or sink heavier than sea water Boundary layer around them replenished with nutrients N Goal to create turbulence Sometimes a cost to sinking loose light not in the photosynthetic zone

6 Phytoplankton Size Classifications
Very small – surface/volume ratio very large to maximize ability to exchange material across surface Picoplankton ( μm) Dominant size in the sea. Nanoplankton (2 – 20 μm) Net plankton ( >> 20 μm) (caught by standard plankton nets) A micrometer or micrometer is an SI unit of length equal to one millionth of a metre, or about a tenth of the size of a droplet of mist or fog. It is also commonly known as a micron. Mm = m Nanoplankton is mostly euk in stomachs of other animals Netplankton is easy to capture in nets, best known in the sea diatoms and dinoflagellates Most of these are able to divide rapidly, populations grow quickly then decrease,

7 Phytoplankton Ecological Classifications
“r strategists” Found where nutrients are pulsed (non-steady) Grow rapidly in resource-poor environments Bloom and bust cycles “K” strategists Steady nutrient concentrations Grow slow in resource-rich environments

8 Major Taxa of the Phytoplankton
Prokaryotes Blue-green algae (cyanobacteria) Other eubacteria (purple sulfur bacteria) Eukaryotes Chromophytes (Golden-brown algae) Diatoms(Bacillariophyceae) Prymnesiophytes Chrysophytes, Cryptophytes Silicoflagellates Chlorophytes (Green algae) Dinoflagellates (Pyrrophyceae) Bacterioplankton free floating bacteris and blue green algae Viroplankton free floating virus Classes listed above Prokaryotes are organisms, such as bacteria and archaea, that lack nuclei and other complex cell structures. In contrast, a eukaryote is an organism with a complex cell or cells, in which the genetic material is organized into a membrane-bound nucleus or nuclei. Eukaryotes comprise animals, plants, and fungi—which are mostly multicellular—as well as protists (many of which are unicellular).Unicellular eukaryotes are those whose members consist of a single cell throughout their life cycle. Microbial eukaryotes can be either haploid or diploid, and some organisms have multiple cell nuclei (see coenocyte). The purple sulfur bacteria are a group of Proteobacteria capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in sulfur springs or stagnant water. Unlike plants and algae, they do not use water as their reducing agent, and so do not produce oxygen. Instead they use hydrogen sulfide, which is oxidized to produce granules of elemental sulfur. This in turn may be oxidized to form sulfuric acid. The purple sulfur bacteria are divided into two families, the Chromatiaceae and Ectothiorhodospiraceae, which respectively produce internal and external sulfur granules, and show differences in the structure of their internal membranes. They make up the order Chromatiales, included in the gamma subdivision of the Proteobacteria. The genus Halothiobacillus is also included in the Chromatiales, in its own family, but it is not photosynthetic. Purple sulfur bacteria are generally found in illuminated anoxic zones of lakes and other aquatic habitats where hydrogen sulfide accumulates and also in "sulfur springs" where geochemically or biologically produced hydrogen sulfide can trigger the formation of blooms of purple sulfur bacteria. The most favorable lakes for the development of purple sulfur bacteria are meromictic (permanently statified) lakes. Meromictic lakes statify because they have denser (usually saline) water in the bottom and less dense (usually freshwater) nearer the surface. If sufficient sulfate is present to support sulfate reduction, the sulfide, produced in the sediments, diffuses upward into the anoxic bottom waters, and here purple sulfur bacteria can form dense cell masses, called blooms, usually in association with green phototrophic bacteria.

9 Autotroph – organisms that can synthesize organic compounds, primary producers
Auxotroph – Phytoplankton that require some organic substrate for growth (vitamins) Vitmains needed include thiamin, biotin, B12 Plan crops double every 2-3 days yet biomass of plants stays the same. Algae have interspecies warfare = Alleopathy plant excretes something that negatively affect another.a diatom Skeletonema needs B12 and excretes thiamin and biotin (conditions water) dinos need properly vitamied water so becaome abundant after a diatom bloom. Algae can put out a pritein that binds the B12, removes it from the water so that the phyto that need it, don’t have it.

10 Cyanobacteria Includes many of the picoplankton, and floaters (lagoon scum) Many do Nitrogen Fixation The smallest are the most abundant phytoplankton in the ocean by far Tropical Cyanobacteria (Greek: κυανόs (kyanós) = blue + bacterium) is a phylum (or "division") of Bacteria that obtain their energy through photosynthesis. They are often still referred to as blue-green algae, although they are in fact prokaryotes like bacteria. The description is primarily used to reflect their appearance and ecological role rather than their evolutionary lineage. Fossil traces of cyanobacteria have been found from around 3.8 billion years ago (b.y.a.). See: Stromatolite. They are a major primary producer in the planetary ocean. Their property to perform oxygenic (plant-like) photosynthesis is thought to have converted the early reducing atmosphere into an oxidizing one, which dramatically changed the life forms on Earth provoking an explosion of biodiversity. Cyanobacteria are found in almost every conceivable habitat, from oceans to fresh water to bare rock to soil. They may be single-celled or colonial. Colonies may form filaments, sheets or even hollow balls. Cyanobacteria include unicellular, colonial, and filamentous forms. Some filamentous colonies show the ability to differentiate into three different cell types: vegetative cells are the normal, photosynthetic cells that are formed under favorable growing conditions; akinetes are the climate-resistant spores that may form when environmental conditions become harsh; and thick-walled heterocysts that contain the enzyme nitrogenase, vital for nitrogen fixation, that may also form under the appropriate environmental conditions (anoxic) wherever nitrogen is necessary. Heterocyst-forming species are specialized for nitrogen fixation and are able to fix nitrogen gas, which cannot be used by plants, into ammonia (NH3), nitrites (NO2−) or nitrates (NO3−), which can be absorbed by plants and converted to protein and nucleic acids. The rice paddies of Asia, which feed about 75% of the world's human population[citation needed], could not do so were it not for healthy populations of nitrogen-fixing cyanobacteria in the rice paddy waters. Each individual cell typically has a thick, gelatinous cell wall, which stains gram-negative. The cyanophytes lack flagella, but may move about by gliding along surfaces. In water column, some of them float due to the ability to form gas vesicles, like in archaea. Most are found in fresh water, while others are marine, occur in damp soil, or even temporarily moistened rocks in deserts. A few are endosymbionts in lichens, plants, various protists, or sponges and provide energy for the host. Some live in the fur of sloths, providing a form of camouflage.

11 Cyanobacteria (pilfered from MIT)
Cyanobacteria have an elaborate and highly organized system of internal membranes which function in photosynthesis. Photosynthesis in cyanobacteria generally uses water as an electron donor and produces oxygen as a by-product, though some may also use hydrogen sulfide as occurs among other photosynthetic bacteria. Carbon dioxide is reduced to form carbohydrates via the Calvin cycle. In most forms the photosynthetic machinery is embedded into folds of the cell membrane, called thylakoids. The large amounts of oxygen in the atmosphere are considered to have been first created by the activities of ancient cyanobacteria. Due to their ability to fix nitrogen in aerobic conditions they are often found as symbionts with a number of other groups of organisms such as fungi (lichens), corals, pteridophytes (Azolla), angiosperms (Gunnera) etc. Cyanobacteria are the only group of organisms that are able to reduce nitrogen and carbon in aerobic conditions, a fact that may be responsible for their evolutionary and ecological success. The water-oxidizing photosynthesis is accomplished by coupling the activity of photosystem (PS) II and I (Z-scheme). In anaerobic conditions, they are also able to use only PS I — cyclic photophosphorylation — with electron donors other than water (hydrogen sulfide, thiosulphate, or even molecular hydrogen) just like purple photosynthetic bacteria. Furthermore, they share an archaebacterial property, which is the ability to reduce elemental sulfur by anaerobic respiration in the dark. Perhaps the most intriguing thing about these organisms is that their photosynthetic electron transport shares the same compartment as the components of respiratory electron transport. Actually, their plasma membrane contains only components of the respiratory chain, while the thylakoid membrane hosts both respiratory and photosynthetic electron transport. Attached to thylakoid membrane, phycobilisomes act as light harvesting antennae for the photosystems . The phycobilisome components (phycobiliproteins) are responsible for the blue-green pigmentation of most cyanobacteria. The variations to this theme is mainly due to carotenoids and phycoerythrins which give the cells the red-brownish coloration. In some cyanobacteria, the color of light influences the composition of phycobilisomes. In green light, the cells accumulate more phycoerythrin, whereas in red light they produce more phycocyanin. Thus the bacteria appear green in red light and red in green light. This process is known as complementary chromatic adaptation and is a way for the cells to maximize the use of available light for photosynthesis. A few genera, however, lack phycobilisomes and have chlorophyll b instead (Prochloron, Prochlorochoccus, Prochlorothrix). These were originally grouped together as the prochlorophytes or chloroxybacteria, but appear to have developed in several different lines of cyanobacteria. For this reason they are now considered as part of cyanobacterial group. (pilfered from MIT)

12 Diatoms Have silica shells appear in sediments
Fast “r” growers in most cases Golden brown color Some toxic (domoic acid) Coastal waters Two forms: pennate, centric Diatoms (Greek: διά (dia) = "through" + τέμνειν (temnein) = "to cut", i.e., "cut in half") are a major group of eukaryotic algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although some form chains or simple colonies. A characteristic feature of diatom cells is that they are encased within a unique cell wall made of silica. These walls show a wide diversity in form, some quite beautiful and ornate, but usually consist of two asymmetrical sides with a split between them, hence the group name. There are more than 200 genera of living diatoms, and it is estimated that there are approximately extant species (Round & Crawford, 1990). Diatoms are a widespread group and can be found in the oceans, in freshwater, in soils and on damp surfaces. Most live pelagically in open water, although some live as surface films at the water-sediment interface (benthic), or even under damp atmospheric conditions. They are especially important in oceans, where they are estimated to contribute up to 45% of the total oceanic primary production (Mann, 1999). Diatoms belong to a large group called the heterokonts, including both autotrophs (e.g. golden algae, kelp) and heterotrophs (e.g. water moulds). Their chloroplasts are typical of heterokonts, with four membranes and containing pigments such as fucoxanthin. Individuals usually lack flagella, but they are present in gametes and have the usual heterokont structure, except they lack the hairs (mastigonemes) characteristic in other groups. Most diatom species are non-motile but some are capable of an oozing motion. As their relatively dense cell walls cause them to readily sink, planktonic forms in open water usually rely on turbulent mixing of the upper layers by the wind to keep them suspended in sunlit surface waters. Some species actively regulate their buoyancy to counter sinking. Some diatoms keep an oil substance to make them boyant and counteract sinking. Diatoms cells are contained within a unique silicate (silicic acid) cell wall comprised of two separate valves (or shells). The biogenic silica that the cell wall is composed of is synthesised intracellularly by the polymerisation of silicic acid monomers. This material is then extruded to the cell exterior and added to the wall. Diatom cell walls are also called frustules or tests, and their two valves typically overlap one other like the two halves of a petri dish. In most species, when a diatom divides to produce two daughter cells, each cell keeps one of the two valves and grows a smaller valve within it. As a result, after each division cycle the average size of diatom cells in the population gets smaller. Once such cells reach a certain minimum size, rather than simply divide vegetatively, they reverse this decline by forming an auxospore. This expands in size to give rise to a much larger cell, which then returns to size-diminishing divisions. Auxospore production is almost always linked to meiosis and sexual reproduction. Decomposition and decay of diatoms leads to organic and inorganic (in the form of silicates) sediment, the inorganic component of which can lead to a method of analyzing past marine environments by corings of ocean floors or bay muds, since the inorganic matter is embedded in deposition of clays and silts and forms a permanent geological record of such marine strata. P 40 Auxospore Resting spore Domoic acid, which causes amnesic shellfish poisoning (ASP), is an amino acid phycotoxin (algal toxin) found associated with certain algal blooms The chemical domoic acid can bioaccumulate in marine organisms that feed on the phytoplankton, such as shellfish, anchovies, and sardines. In mammals, including humans, domoic acid acts as a neurotoxin, causing short-term memory loss, brain damage, and death in severe cases. Red tides are associated with the phenomenon of ASP. Considerable recent research has been carried out by the Marine Mammal Center and other scientific centers on the association of red tides to domoic acid and to resulting neurological damage in marine mammals of the Pacific Ocean. In the brain, domoic acid especially damages the hippocampus and amygdaloid nucleus. It damages the neurons by activating AMPA and kainate receptors, causing an influx of calcium. Although calcium flowing into cells is a normal event, the uncontrolled increase of calcium causes the cell to degenerate.


14 Diatom Skeletons (tests)
Centric Pennate The classification of heterokonts is still unsettled, and they may be treated as a division (or phylum), kingdom, or something in-between. Accordingly, groups like the diatoms may be ranked anywhere from class (usually called Bacillariophyceae) to division (usually called Bacillariophyta), with corresponding changes in the ranks of their subgroups. Diatoms are traditionally divided into two orders: centric diatoms (Centrales), which are radially symmetric, and pennate diatoms (Pennales), which are bilaterally symmetric. The former are paraphyletic to the latter. A more recent classification is that of Round & Crawford (1990), who divide the diatoms into three classes: centric diatoms (Coscinodiscophyceae), pennate diatoms without a raphe (Fragilariophyceae), and pennate diatoms with a raphe (Bacillariophyceae). It is probable there will be further revisions as our understanding of their relationships increases. In phylogenetics, a group of organisms is said to be paraphyletic (Greek para = near and phyle = race) if the group contains its most recent common ancestor, but does not contain all the descendants of that ancestor. Groups that do include all the descendants of the most recent common ancestor are commonly said to be monophyletic.

15 Prymnesiophytes Includes coccolithophorids (with CaCO3 shells) which form sediments Golden brown color Motile, flagellates Oceanic Some are toxic (problem in Scandinavia) Coccolithophores are single-celled algae, or phytoplankton, belonging to the haptophytes. They are distinguished by special calcium carbonate plates (or scales) of unknown purpose called coccoliths, which are important microfossils. Coccolithophores are exclusively marine and are found in large numbers throughout the surface euphotic zone of the ocean. An example of a globally significant coccolithophore is Emiliania huxleyi. Due to their microscopic size and broad distribution of many taxa, coccoliths (calcareous nannoplankton) have become very popular for solving various stratigraphic problems, and many studies have been devoted to that end. Nanofossils are sensitive indicators of changes in the temperature and salinity of the ocean and sea surface water. Quantitative analysis of calcareous nanoplankton assemblages is being employed to reveal such changes.

16 Coccolithophorid bloom off Newfoundland
We now understand further that these white waters are brought about by the coccoliths (not the organic cells themselves) which act like minute (smaller than pinhead-sized) mirrors suspended in the water. En masse they cause a significant amount of the incoming sunlight to be reflected back out of the water. Water containing large amounts of coccoliths is optically similar to water if sackloads of glitter or sequins were to be added to it. This property of the blooms makes Ehux uniquely accessible to scientific investigation - the reflectance from the blooms can be picked up by satellites in space, allowing the extent of the blooms of this single species to be distinguished in fine detail. The presence of chlorophyll in the water can be detected by satellite, but this does not tell us which individual phytoplankton species or set of species is responsible. In contrast, the presence of coccoliths can be detected separately, delineating precisely the extent of a coccolithophore bloom: When water conditions are favourable, it has the capacity to occur in massive blooms, sometimes > 100,000 square kilometres (the size of England) in extent. During these blooms the numbers of Ehux cells usually outnumber those of all other species combined, frequently accounting for 80 or 90% or more of the total number of phytoplankton cells in the water. The cells are accompanied by even larger numbers of coccoliths; many of them attached to the cells but also many floating separately in the water. The freely floating coccoliths are thought to arise due to over-production of coccoliths leading to the synthesis of more than can be securely held on the cell surface. Other possible causes are death of the cell after which the empty coccospheres disintegrate, and asexual cell division after which the coccosphere must presumably break open to let out one or both of the two inhabitants. Ehux may well be unique amongst the coccolithophores in its generation of so many free coccoliths. SeaWiFS Project and ORBIMAGE

17 Chlorophytes Green in color Rare in the ocean Can be motile
Related to higher plants and land plants The Chlorophyta, or green algae, include about 8000 species[1] of mostly aquatic photosynthetic eukaryotic organisms. Like the land plants (Bryophyta and Tracheophyta), green algae contain chlorophylls a and b, and store food as starch in their plastids. They are related to the Charophyta and Embryophyta (land plants), together making up the Viridiplantae. They contain both unicellular and multicellular species. While most species live in freshwater habitats and a large number in marine habitats, other species are adapted to a wide range of environments. Watermelon snow, or Chlamydomonas nivalis, of the class Chlorophyceae, lives on summer alpine snowfields. Others live attached to rocks or woody parts of trees. Some lichens are symbiotic relationships with fungi and a green alga. Members of the Chlorophyta also form symbiotic relationships with protozoa, sponges and coelenterates.

18 Dinoflagellates Motile (2 flagellae), can have a test (cellulose-like)
Many are toxic Most red tides are dinoflagellates All waters, esp. warm Are also often symbionts of benthic and pelagic “heterotrophs” Autotrophic Heterotrophic Dormant cysts Phytoplankton blooms Red tides Most dinoflagellates are unicellular forms with two dissimilar flagella. One of these extends towards the posterior, called the longitudinal flagellum, while the other forms a lateral circle, called the transverse flagellum. In many forms these are set into grooves, called the sulcus and cingulum. The transverse flagellum provides most of the force propelling the cell, and often imparts to it a distinctive whirling motion, which is what gives the name dinoflagellate refers to (Greek dinos, whirling). The longitudinal acts mainly as the steering wheel, but providing little propulsive force as well. Life-cycle Dinoflagellates have a peculiar form of nucleus, called a dinokaryon, in which the chromosomes are attached to the nuclear membrane. These lack histones and remained condensed throughout interphase rather than just during mitosis, which is closed and involves a unique external spindle. This sort of nucleus was once considered to be an intermediate between the nucleoid region of prokaryotes and the true nuclei of eukaryotes, and so were termed mesokaryotic, but now are considered advanced rather than primitive traits. In most dinoflagellates, the nucleus is dinokaryotic throughout the entire life cycle. They are usually haploid, and reproduce primarily through fission, but sexual reproduction also occurs. This takes place by fusion of two individuals to form a zygote, which may remain mobile in typical dinoflagellate fashion or may form a resting dinocyst, which later undergoes meiosis to produce new haploid cells. However, when the conditions become desperate, usually starvation or no light, their normal routines change dramatically. Two dinoflagellates will fuse together forming a planozygote. Next is a stage not much different from hibernation called hypnozygote when the organism takes in excess fat and oil. At the same time its shape is getting fatter and the shell gets harder. Sometimes even spikes are formed. When the weather allows it, these dinoflagellates break out of their shell and are in a temporary stage, planomeiocyte, when they quickly reforms their individual thecae and return to the dinoflagellates at the beginning of the process.

19 Zooxanthellae Algae → protection, nitrogen and carbon dioxide Anemones
→ oxygen and nourishment Three local species of closely-related sea anemones all have brownish-colored algae (zooxanthellae) growing in their tissues. They are essentially plant-animals. The algae gain protection, nitrogen and carbon dioxide from the anemones and give the anemones oxygen and nourishment in return. The anemones open and close to regulate the amount of light the algae receive and also produce greenish fluorescent pigments that apparently protect the algae. These animal pigments give the animals their greenish coloration, not the algae. (North of Bodega some anemones also contain green algae (zoochlorellae) that give them a grass-green color.) All three species reproduce sexually; they have separate sexes and in the summer, release eggs and sperm into the sea where fertilization and larval development occurs.

20 Dinoflagellates Ceratium Dinophysis
Paralytic shellfish poisoning (PSP) is one of the four recognised syndromes of shellfish poisoning (the others being neurologic shellfish poisoning, diarrheal shellfish poisoning and amnesic shellfish poisoning). All four syndromes share some common features and are primarily associated with bivalve molluscs (such as mussels, clams, oysters and scallops). These shellfish are filter feeders and, therefore, accumulate toxins produced by microscopic algae in the form of dinoflagellates and diatoms. Pathophysiology The toxins responsible for most shellfish poisonings are water-soluble, heat and acid-stable, and are not inactivated by ordinary cooking methods. The main toxin responsible for PSP is principally saxitoxin, but also gonyautoxin. The saxitoxins act by blocking sodium ion movement through voltage-dependent sodium channels in nerve and muscle cell membranes. Conduction block occurs principally in motor neurons and muscle. The toxin is made by dinoflagellates of the genus Gonyaulax which create the conditions known as "red tide". Almost all bivalve molluscs such as clams, mussels, oysters, snails and scallops ingest these organisms while feeding, and the poison is stored in their bodies. Most shellfish only store this toxin for six weeks after a red tide passes, but some such as butterclams are known to store the toxin for up to two years. PSP can be fatal in extreme cases (particularly those already immuno-suppressed). Children are more susceptible. PSP affects those who come into contact with the affected shellfish by ingestion. Ten to thirty minutes after ingestion, symptoms can include nausea, vomiting, diarrhea, abdominal pain, and tingling or burning lips, gums, tongue, face, neck, arms, legs, and toes. Shortness of breath, dry mouth, a choking feeling, confused or slurred speech, and lack of coordination are also possible. Urban legends in upper Australia and Indonesia report victims of paralytic shellfish poisoning being mistaken for dead, and being hastily interred or luckily recovering sufficiently to give a signal during the funeral. Ceratium Dinophysis

21 Asexual reproduction is the most common way of making more dinoflagellates.
In asexual reproduction the haploid parent cell undergoes mitosis, producing two identical daughter cells. During this process the theca may be discarded or retained, with each daughter cell keeping one half and regrowing the other half. Sexual reproduction is also observed in dinoflagellates. Because the adult, motile cells are haploid (1N), they form their gametes via mitosis, resulting in either a naked or armored, free swimming, miniature version of the parent cell. When the flagella of the male and female gametes become entangled, they fuse to form a diploid (2N) planozygote, an actively swimming zygote. The planozygote then enlarges, developing into a diploid hypnozygote, or resting cyst that is provisioned with food reserves and sometimes toxins. The resting cyst sinks to the ocean floor where they remain dormant during the winter for at least four months. The hypnozygote finally undergoes meiosis, restoring the haploid motile cell. Temporary cysts are not involved in reproduction. They form when dinoflagellates experience stressful conditions, such as cold temperature. However, when reintroduced to favorable conditions they reconvert to the motile stage within hours. Gonyaulax

22 Dinoflagellate Red Tide
Red tide is a common name for a phenomenon known as an algal bloom, an event in which estuarine or marine algae accumulate rapidly in the water column, or "bloom". These algae, more correctly termed phytoplankton, are microscopic, single-celled, plant-like organisms that can form dense, visible patches near the water's surface. Certain species of phytoplankton contain photosynthetic pigments that vary in color from green to brown to red, and when the algae are present in high concentrations, the water appears to be colored red. Not all algal blooms are dense enough to cause water discoloration, and not all discolored waters associated with algal blooms are red. Additionally, red tides are not typically associated with tidal movement of water, hence the preference among scientists to use the term algal bloom. The term "red tide" is most often used to describe a particular type of algal bloom common to the eastern Gulf of Mexico, and is also called "Florida red tide". This type of bloom is caused by a species of dinoflagellate known as Karenia brevis, and these blooms occur almost annually along Florida waters. The density of these organisms during a bloom can exceed tens of millions of cells per liter of seawater, and often discolor the water a deep reddish-brown hue. The most conspicuous effects of red tides are the associated wildlife mortalities among marine and coastal species of fish, birds, marine mammals and other organisms. In the case of Florida red tides, these mortalities are caused by exposure to a potent neurotoxin produced naturally by Karenia brevis, called brevetoxin. It is unclear what causes red tides, but the frequency and severity of algal blooms in many parts of the world have been linked to increased nutrient loading from human activities. The growth of marine phytoplankton is generally limited by the availability of nitrates and phosphates, which can be abundant in agricultural run-off. Costal water pollution produced by humans and systematic increase in sea water temperature have also been implicated as contributing factors in red tides. On the Pacific Coast of the U.S. there have been apparent increases in the occurrence of red tides since about These increases are correlated with a marine temperature rise of about one degree Celsius, and also with increased nutrient loading into ocean waters. Other factors such as iron-rich dust influx from large desert areas such as the Saharan desert are thought to play a major role in causing red tides. Some algal blooms on the Pacific coast have also been linked to occurrences of large-scale climatic oscillations such as El Niño events. While red tides in the Gulf of Mexico have been occurring since the time of early explorers such as Cabeza de Vaca it is unclear what initiates these blooms, and how large a role anthropogenic and natural factors play in their development. Algal blooms in many parts of the world cannot be reasonably linked to human influence, and are generally accepted as a natural occurrence. It is also debated whether the apparent increase in frequency and severity of algal blooms in various parts of the world is in fact a real increase or is due to increased effectiveness of monitoring programs and species identification ability. Some red tide organisms produce large quantities of toxins, such as saxitoxin, ciguatoxin, and brevetoxin, which disrupt the proper function of ion channels in neurons. Domoic acid, a toxin produced by diatoms of the genus Pseudonitzschia, has been linked to neurological damage in certain marine mammals, and is frequently found in algal blooms on the U.S. West Coast. Some red tide toxins can become highly concentrated in various marine organisms that have the ability to filter and consume large quantities of toxic plankton directly from seawater. These include shellfish, finfish, baleen whales, and benthic crustaceans. Frequently, shellfish collected in areas affected by algal blooms can be potentially dangerous for human consumption, leading to closures of shellfish beds for harvesting. Initial signs of shellfish poisoning from red tide toxins such as domoic acid is tingling in the lips followed by a reduction of motor abilities and difficulty breathing and can be fatal if consumed in sufficient amounts. If these symptoms occur after eating shellfish, seek immediate medical treatment. Standard medical treatment is to give victims oxygen, or to hook them up to a breather. There exists no antidote, and the idea is to keep the person alive until the toxin has passed from the system.

23 La jolla Scripps pier

24 Dinoflagellate Symbionts
Many cnidaria (corals, anenomes) have dinoflagellate symbionts called zooxanthellae. Also many species of planktonic protists (radiolaria, acantharia, foraminifera) Coral reef bleaching, the whitening of diverse invertebrate taxa, results from the loss of symbiotic zooxantheallae and/or a reduction in photosynthetic pigment concentrations in zooxanthellae residing within scleractinian corals. Coral reef bleaching is caused by various anthropogenic and natural variations in the reef environment including sea temperature, solar irradiance, sedimentation, xenobiotics, subaerial exposure, inorganic nutrients, freshwater dilution, and epizootics. Coral bleaching events have been increasing in both frequency and extent worldwide in the past 20 years. Global climate change may play a role in the increase in coral bleaching events, and could cause the destruction of major reef tracts and the extinction of many coral species. Corals live in very nutrient poor waters and have certain zones of tolerance to water temperature, salinity, UV radiation, opacity, and nutrient quantities.  Scleractinian corals build skeletons of calcium carbonate sequestered from the water. When the coral polyp dies, this skeleton remains incorporated in the reef framework.   Scleractinian corals are in the Phylum Cnidaria, and they receive their nutrient and energy resources in two ways. They use the traditional cnidarian strategy of capturing tiny planktonic organisms with their nematocyst capped tentacles, as well as having a obligate symbiotic relationship with a single cell algae known as zooxanthellae. Zooxanthellae are autorophic microalgaes belonging to various taxa in the Phylum Dinoflagellata.  Zooxanthellae live symbiotically within the coral polyp tissues and assist the coral in nutrient production through its photosynthetic activities. These activities provide the coral with fixed carbon compounds for energy, enhance calcification ,and mediate elemental nutrient flux. The host coral polyp in return provides its zooxanthellae with a protected environment to live within, and a steady supply of carbon dioxide for its photosynthetic processes. The symbiotic relationship allows the slow growing corals to compete with the faster growing multicellular algaes because the tight coupling of resources and the fact that the corals can feed by day through photosynthesis and by night through predation.   The tissues of corals themselves are actually not the beautiful colors of the coral reef, but are instead clear. The corals receive their coloration from the zooxanthellae living within their tissues. Disturbances affecting coral reefs include anthropogenic and natural events. Recent accelerated coral reef decline seems to be related mostly to anthropogenic impacts (overexploitation, overfishing, increased sedimentation and nutrient overloading. Natural disturbances which cause damage to coral reefs include violent storms, flooding, high and low temperature extremes, El Nino Southern Oscillation (ENSO) events, subaerial exposures, predatory outbreaks and epizootics.  Coral reef bleaching is a common stress response of corals to many of the various disturbances mentioned above. Beginning in the 1980s, the frequency and widespread distribution of reported coral reef bleaching events increased. Widespread bleaching, involving major coral reef regions and resulting in mass coral mortality has raised concerns about linkage of the events to global phenomenons including global warming or climate change and increased UV radiation from ozone depletion. This paper examines the causes of coral reef bleaching and addresses the impact of global climate change on coral reefs.   Coral reef bleaching  Bleaching, or the paling of zooxanthellate invertebrates, occurs when (i) the densities of zooxanthellae decline and / or (ii) the concentration of photosynthetic pigments within the zooxanthellae fall (Kleppel et al. 1989). Most reef-building corals normally contain around 1-5 x 106 zooxanthellae cm-2 of live surface tissue and 2-10 pg of chlorophyll a per zooxanthella. When corals bleach they commonly lose 60-90% of their zooxanthellae and each zooxanthella may lose 50-80% of its photosynthetic pigments (Glynn 1996). The pale appearance of bleached scleractinian corals and hydrocorals is due to the cnidarian’s calcareous skeleton showing through the translucent tissues (that are nearly devoid of pigmented zooxanthellae). If the stress-causing bleaching is not too severe and if it decreases in time, the affected corals usually regain their symbiotic algae within several weeks or a few months. If zooxanthellae loss is prolonged, i.e. if the stress continues and depleted zooxanthellae populations do not recover, the coral host eventually dies .  Three hypotheses have been advanced to explain the cellular mechanism of bleaching, and all are based on extreme sea temperatures as one of the causative factors. High temperature and irradiance stressors have been implicated in the disruption of enzyme systems in zooxanthellae that offer protection against oxygen toxicity. Photosynthesis pathways in zooxanthallae are impaired at temperatures above 30 degrees C, this effect could activate the disassociation of coral / algal symbiosis. Low- or high-temperature shocks results in zooxanthellae low as a result of cell adhesion dysfunction. This involves the detachment of cnidarian endodermal cells with their zooxanthellae and the eventual expulsion of both cell types.  It has been hypothesized that bleaching is an adaptive mechanism which allows the coral to be repopulated with a different type of zooxanthellae, possibly conferring greater stress resistance. Different strains of zooxanthellae exist both between and within different species of coral hosts, and the different strains of algae show varied physiological responses to both temperature and irradiance exposure. The coral / algal association may have the scope to adapt within a coral’s lifetime. Such adaptations could be either genetic or phenotypic. Solar Irradiance  Bleaching during the summer months, during seasonal temperature and irradiance maxima often occurs disproportionately in shallow-living corals and on the exposed summits of colonies. Solar radiation has been suspected to play a role in coral bleaching. Both photosyntheticaly active radiation (PAR, nm) and ultraviolet radiation (UVR, nm) have been implicated in bleaching. 

25 Long exposure image of red tide bioluminescence taken at midnight at a Carlsbad, California beach during the 2005 red tide event. Image taken by Flickr user msauder. Original caption: "Bioluminescent dinoflagellates (Lingulodinium polyedrum) lighting a breaking wave at midnight. The blue light is a result of a luciferase enzyme (like firefly luciferase, but the enzyme in L. polyedrum shares no similarity with that of the firefly enzyme). Under the right conditions, the dinoflagellates become so numerous that the water takes on a muddy reddish color (hence the name "Red Tide"). The bioluminescence is only visible at night. The photo was taken 6/26/2005

26 Chlorophyl flouresence SST (purple colder)

Download ppt "Environmental Processes in Oceans and Lakes"

Similar presentations

Ads by Google