Marine Ecology May 19 2008 EpipelagicAntarctic Marine Ecosystem

Marine Ecology, May 19, 2008 Epipelagic/Antarctic Marine Ecosystem, Part 1

The epipelagic zone n Epipelagic Ø Upper pelagic, within photic zone n Neritic Ø Waters on the continental shelves n Oceanic Ø Waters beyond the shelf break

Epipelagic food web(simplified)

“Classic” food chain vs. microbial loop

Phytoplankton types 1 n Free-floating photosynthetic Bacteria and Archaea Cyanobacteria Photosynthetic Archaea

Phytoplankton types 2 n Photosynthetic Protista Diatoms: have silicaceous “frustules”; many form chains Prymnesiophytes (i. e. Phaeocsytis) exist as single cells or colonies Dinoflagellates have two flagella Cryptophytes are single and small

Global primary productivity: marine

Factors affecting phytoplankton growth n n n Light Nutrients Location of the pycnocline Temperature Role of ice in polar regions

Light levels as a function of latitude

Nutrients (inorganic) n Nutrient sources ØUpwelling: n coastal and equatorial; n Edges of islands and reefs ØDeep mixing by winter storms n Examples: Key in Pacific Northwest, Antarctica ØRunoff from land n Example: In Antarctica, bird and seal colonies produce nutrient-rich waste

Nutrients n Nutrient sinks ØNutrients consumed by primary producers ØUneaten phytoplankton, consumers and their fecal material sink out of photic zone

Which is limiting, nutrients or light? (Very simplified…) n In Antarctic, ØLight-limited through much of year ØPossibly nutrientlimited later in the season… n Affects phytoplankton community composition

Pycnocline: location and stability n Shallow, stable pycnocline promotes phytoplankton growth

Pycnocline: location and stability

Temperate ocean (i. e. Oregon) *Shallow pycnocline: late spring through summer. Causes?

Polar ocean (i. e. Antarctica) *This shows open water. What about iceassociated areas?

Ice! n n Role in pycnocline set-up and stability Role in “seeding” ice edge blooms

Seasonal variation in ice cover (Parkinson et al. , 1998)

Variability in phytoplankton community composition n Both spatial and temporal variations. ØWhy? n Varying light levels n Varying nutrients n Presence in water column or ice ØExample: Phaeocystis vs. diatoms in Antarctic phytoplankton blooms

Zooplankton: overview n Key crustacean zooplankters Ø Copepods

Zooplankton: overview n Key crustacean zooplankters ØKrill!

Zooplankton: overview n Gelatinous zooplankters Salps (above) and larvaceans (below) both feed on picoplankton and nanoplankton Ctenophores are predators of other zooplankters

Beware of Beröe! n Feeds on other ctenophores; appears to reduce their negative impacts!

Antarctic marine food web (simplified)

Focus on krill! n n n Basic anatomical features Feeding behavior Food selectivity (briefly) Ø Primarily herbivores; feed preferentially on diatoms compared to Phaeocystis! Ø Winter omnivory? n n Schooling Life History

Life history basics Nauplius

Furcilia and juveniles (mostly) feeding beneath the ice

Declining krill? Or not…? (Angus Atkinson, 2004, Science)

Focus: Antarctic penguins Gentoo penguins (Photo: B. Grunewald) Chinstrap penguin (Photo: Shir Goldberg Adelie penguins (Photo: K. Haberman)

Adaptations for swimming, diving, cold water & snow n n Solid bones Hindlimb Ø Rearward rotation Ø Webbed feet Ø Claws n Forelimbs Ø Modified as paddles n n Air sacs: reduced Other…

Shift in penguin species on the Antarctic Peninsula

Black-browed albatross n Feeds primarily on krill! Black-browed albatross Photo: K. Haberman

Southern giant petrel n n Feeds primarily on krill “Gack” defense by young Southern giant petrel Photo: K. Haberman

Wilson’s storm petrel n “Jesus birds”: feed on near-surface zooplankton (smaller krill species, copepods, amphipods) Wilson’s storm petrel Photo: K. Haberman

Blue-eyed shag (cormorants) n n Feed on fish and squid; deep divers Have heavy bones like penguins Blue-eyed shag Photos: K. Haberman

Kelp gulls n Limpet eaters! Kelp gulls Photo: K Haberman

Order Pinnipedia, Family Phocidae Crabeater seal Photo: Karen Haberman

Crabeater seal skull showing krill eater teeth!

Elephant seals

Order Pinnipedia, Family Phocidae Leopard seal Photo: Karen Haberman

Order Pinnipedia, Family Phocidae Weddell seal Photo: Karen Haberman

Order Pinnipedia, Family Otariidae Southern fur seal (related to sea lions) Photo: Karen Haberman

Order Cetacea; Suborder Mysticeti Humpback Whale Photo: K. Haberman

Order Cetacea; Suborder Mysticeti Minke Whale Photo: Project Atlantis

Order Cetacea; Suborder Mysticeti Blue Whale Photo: Project Atlantis

Order Cetacea; Suborder Odontoceti Family Delphinidae Orca Photo: NOAA