sea otter - review of last lecture

The last of the otters 150 years after excessive hunting, by late 1800s, only 3000 otters left 150 years after excessive hunting, by late 1800s, only 3000 otters left International Fur Treaty established in 1911: illegal to kill sea otters, even for indigenous Alaskans International Fur Treaty established in 1911: illegal to kill sea otters, even for indigenous Alaskans

Otters repopulate In 1980s, census conducted: 150,000 otters on earth, mostly in Alaska In 1980s, census conducted: 150,000 otters on earth, mostly in Alaska 2000 otters found in California, population was thought to be extinct there 2000 otters found in California, population was thought to be extinct there Sea otters give birth to 1 infant per pregnancy, 6 month gestation Sea otters give birth to 1 infant per pregnancy, 6 month gestation

A new threat emerges In 1991, first killer whale attack on Alaskan otter is witnessed In 1991, first killer whale attack on Alaskan otter is witnessed

Sequential overharvesting of marine mammals Killer whales may have switched to otters because their normal food (whales and seals) has become rare. Killer whales may have switched to otters because their normal food (whales and seals) has become rare.

KELP FORESTS

What Charles Darwin said … “ I can only compare these great aquatic forests … with the terrestrial ones in the intertropical region. Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of the kelp. Amidst the leaves of this plant numerous species of fish live, which nowhere else could find food or shelter …” Charles Darwin, 1 June 1834, Tierra del Fuego, Chile

Outline Kelp structure and function Kelp structure and function Kelp ecosystem biodiversity Kelp ecosystem biodiversity Change of kelp through time Change of kelp through time Human destruction of kelp Human destruction of kelp Kelp forests in the future Kelp forests in the future Role of sea otters as keystone species Role of sea otters as keystone species Urchin barrens Urchin barrens

Kelp (Brown Algae) Brown Algae (Phaeophyta) 1000 species, almost all marine 1000 species, almost all marine Includes Sargassum, Padina, kelps Includes Sargassum, Padina, kelps Most common in cold, temperate seas Most common in cold, temperate seas Two pigments for photosynthesis: Two pigments for photosynthesis: 1) Chlorophyll a (like all plants) 2) Fucoxanthin (brown color)

Kelp: Division Phaeophyta (Brown Algae) Parts of a kelp Gas-filled pneumatocysts Gas-filled pneumatocysts Rootlike holdfast to attach to substrate Rootlike holdfast to attach to substrate Long hollow stem or stipe Long hollow stem or stipe Leaflike blades Leaflike blades Complex life cycle Complex life cycle

FUNCTION AND FORM

Kelp “life history” Kelp alternates between a large sporophyte and a tiny gametophye - sporophyte = “plant that makes spores” - sporophyte = “plant that makes spores” (diploid, 2N, large plant-like stage) - gametophyte = “plant that makes gametes” (haploid, 1N, small inconspicous stage - can be a tiny thread) /botany/browns/james/Web/li fehis.htm /botany/browns/james/Web/li fehis.htm

Kelp forest zonation

Giant Kelps - largest of all algae Kelp Forests One plant can grow m in one season One plant can grow m in one season Can reach 45 m long Can reach 45 m long Among most productive of all plant communities Among most productive of all plant communities Subtidal to 20 meters Subtidal to 20 meters Like cold water Like cold water

Kelp forests - Where do they occur? Cold, temperate water Kelp forests are more common off West Coast of N. America than E. Coast Why?

Kelp forests - Where do they occur? Giant kelp forests More common off West Coasts of N. America than E. Coast because of cool California current off Ca coast vs.warm Gulf Stream on East Coast

Figure Kelp forests occur in cool water

Kelp diversity Low taxonomic diversity Low taxonomic diversity (few species of kelp) High structural and functional diversity High structural and functional diversity (many shapes and creates many different architectural habitats that promote diversity of associated organisms)

The ecological role of kelp

Dampen wave action Reduce coastal erosion Enhance recruitment of fish and invertebrates High productivity and turnover of plant matter puts many nutrients into system High structural diversity (like a forest on land) provides shelter and habitat for many species Habitat complexity created: - understory with filtered light - canopy at surface

Animals of the kelp forest

Kelp forests come and go…

Kelp forests vs terrestrial forests

Similarities and differences to terrestrial forests Both forest types: Recruitment and growth depends upon canopy breaks for available light Structure similar - different canopy levels, varied understory Form foundation for large diversity of animals and plants Both are primary producers, get their energy from the sun Kelp forests have shorter life spans, shorter heights Kelp forests are faster growing, shorter-lived: Few kelp sp. last more than 25 years Terr. forest trees can live for thousands of years Kelp forests are more diverse in terms of number of animal phyla, less in terms of animal species? Terrestrial forests are habitat for roughly 3 phyla Kelp forests are habitat for 10 or more phyla

Kelp forests are deforested by natural causes Salinity, temperature change, storms, seasons Can recover fairly quickly under natural conditions

Sea urchins graze on kelp

Sea otters control urchin populations by eating them

Rise of urchins through time

CALIFORNIA CA kelp forests considered most diverse in world CA kelp forests considered most diverse in world Exploited for past ,000 yrs Exploited for past ,000 yrs Shell middens from aboriginal people show decrease in animal size with hunting Shell middens from aboriginal people show decrease in animal size with hunting

Animals begin to disappear from kelp forests Otters functionally gone by early 1800s Kelp forest ecosystem persisted for next 150 years Probably because other predators, like fish, compensated by increasing in numbers and eating urchins

White sea bass landings

CA kelp begins to change CA kelp forest so diverse, other predators keep urchins in check even with few otters CA kelp forest so diverse, other predators keep urchins in check even with few otters Continues to persevere for another 150 years Continues to persevere for another 150 years Now in trouble - not so diverse Now in trouble - not so diverse

Kelp forest changes

Kelp conservation status Climate change (global temp. increase), human pop. growth, coastal development, oil spills, overfishing impacts, non-native sp. invasions all predicted to increase over next 25 years Climate change (global temp. increase), human pop. growth, coastal development, oil spills, overfishing impacts, non-native sp. invasions all predicted to increase over next 25 years Currently, in some areas fisheries for urchins coincide with fisheries for urchin predators – a delicate balance Currently, in some areas fisheries for urchins coincide with fisheries for urchin predators – a delicate balance Not all areas will be affected in future by temperature changes, but – mean annual global temperature predicted to increase (last century 1 degree C increase in global air temp) Not all areas will be affected in future by temperature changes, but – mean annual global temperature predicted to increase (last century 1 degree C increase in global air temp)

NORTH PACIFIC/ALASKA Sea otters, sea cows, sea Sea otters, sea cows, sea urchins and humans urchins and humans

History of fishing in N. Pacific Colonization 30,000 years ago, boats used off Japan coast for past 25,000 years Colonization 30,000 years ago, boats used off Japan coast for past 25,000 years Stellar’s sea cow hunted to extinction (35 feet long, several tons) Stellar’s sea cow hunted to extinction (35 feet long, several tons)

History of fishing in Alaska Humans in Alaska for ,000 years. Indigenous tribes began to hunt otters ~ 2500 years ago. Otter hunting intensified with European arrival in 1700s. Ecosystem changed to urchin dominated.

Otters and urchins

NORTH ATLANTIC Sea urchins and kelp, but no sea otters, but very large predatory fish! Sea urchins and kelp, but no sea otters, but very large predatory fish!

Cod fishery intense for centuries

Urchins rise again Fishing technology decreases cod pop. by 1930s Fishing technology decreases cod pop. by 1930s

A sign of things to come

CONCLUSION Kelp forests are home and nurseries for much marine life Kelp forests are home and nurseries for much marine life Kelp forests could disappear or become functionally extinct within decades in absence of effective management that takes complex ecosystem into effect, including direct and indirect effects (eg, overhunting of whales leads to killer whale predation on sea otters, leads to rise of urchins and death of kelp) Kelp forests could disappear or become functionally extinct within decades in absence of effective management that takes complex ecosystem into effect, including direct and indirect effects (eg, overhunting of whales leads to killer whale predation on sea otters, leads to rise of urchins and death of kelp)

References Dayton, PK, Tegner MJ, Edwards PB, et al Sliding baselines, ghosts, and reduced expectations in kelp forest communities ECOL APPL 8 (2): MAY 1998 Estes, JA, Duggins, DO, Rathbun, GB. The ecology of extinctions in kelp forest communities. CONSERV BIOL 3 (3): SEP 1989 Jackson, JBC, Sala E Unnatural oceans SCI MAR 65: Suppl. 2 SEP 2001 Jackson, JBC, Kirby, MX, Berger, WH, et al. Historical overfishing and the recent collapse of coastal ecosystems SCIENCE 293 (5530): JUL Jackson, JBC What was natural in the coastal oceans? P NATL ACAD SCI USA 98 (10): MAY Simenstad CA, Estes JA, Kenyon KW. Aleuts, sea Otters, and alternate stable-state communities SCIENCE 200 (4340): Steneck RS, Graham MH, Bourque BJ, et al. Kelp forest ecosystems: biodiversity, stability, resilience and future ENVIRON CONSERV 29 (4): DEC 2002 Tegner, MJ, Dayton, PK Sea-urchins, El-Ninos, and the long-term stability of southern California kelp forest communities MAR ECOL-PROG SER 77 (1): OCT 1991