Lecture 19: Coastal and Polar

• Continental shelves make up about 7% of the ocean's floors
• Coastal shelves responsible for 20% of ocean's primary production and 90% of the world's fisheries
• The average length of a continental shelf is 40 miles
• Continental shelves have high primary productivity due to shallow water, sunlight, abundant nutrients, benthic bacteria/nutrient coupling
• Fisheries productive in shelves due to proximity to land (nutrient source and proximity to harvesters)
• Neritic waters are highly productive due to rapid phytoplankton turnover, which supports a larger primary consumer biomass, which then support larger populations of high order consumers
• Zooplankton are very important in coastal food chains
• Continental oceans support about 20% of ocean production
• Sediments are coarser where current flow is high and finer where current flow is low
• General trend in sediment where sand becomes finer with depth
• Hard and Soft Bottom Communities:

  hard: dominated by sessile colonial organisms (sponges, bryozoans, hydroids, tunicates)

  soft: dominated by suspension feeders (sand) and deposit feeders (mud)
• Patchiness of benthic communities due to sunlight, sediment type, shifting sediments/currents, and larval settlement
• Infaunal found in finer sands within the mud
• Epifaunal found in coarser sands on the outside
• Continental shelf fishes: Gadiforms, Scorpaeniforms, Pleuronectiformes
• Kelp forests are found in cold temperate climates on the rocky inshores, giant brown algae
• Kelp forest community structure:

  Substrate, Understory, Canopy
• Canopy in kelp forests contain long stipes
• Understory of kelp forests contain shorter stipes and low light conditions
• Substrate in kelp forests contain encrusting algaes
• Kelp forests contain many epiphytes, detritus, and direct grazers (like the Garibaldi fish)
• Inverse relationship between kelp and sea urchins
• Polar seas in the Arctic and Antarctic are dominated by ice and snow, year-round cold temperatures, drastic changes in photoperiod that prevent photosynthesis for part of the year
• The Arctic is ice-covered and surrounded by continents
• The Antarctic is a frozen continent surrounded by ice-covered sheets
• Much of the Arctic is permanently covered with ice, resulting in low primary production
• Around the Antarctic, upwelling occurs supporting a high summertime primary productivity
• Polar seas have shallow water communities that are rarely disturbed by wave action.
• Physical stress in Polar Seas is ice motion. Ice formation can disrupt the water column.
• The Antarctic is richer in species of benthic organisms, high level of enedmism, and a high level of biomass
• The Arctic is impoverished and consists of organisms derived from the Atlantic Ocean
• The Antarctic is more productive than the Arctic due to upwelling of nutrient rich water, less salinity variation, and less scouring of benthos by ice
• Polar seas dominated by diatoms, but about 200 species live in the sea ice.
• The Nototheniid fish contains it's own anti-freeze to help deal with the cold water temperatures and prevent their bodies from freezing