OCEAN: Chapter 15 - Benthic Animals

Chemosynthetic archea

Vent Archaea (ancient group of simple-like bacteria, Woese et al., 1990) *Do not form the base of the food web at cold water reefs.* Archea are found: - within the vent chimneys (but not at temperatures above 110°C) - symbiotically within host organisms (worms, clams, mussels) - bacterial mats coating the sea-bed

Lobster

*- Belong to genus "homarus" - Do not eat oysters - Panulirus Argus exhibits a behavior of migrating single file across the sea floor in lines that are several kilometers long.*

Coral reef distribution/zonation

*Deep-water corals lack the symbiotic zooxanthellae algae that their shallow-water cousins have.* *Temperature must be between 18-30; Water warm enough to support coral growth is found primarily in the tropical regions of the oceans.* *Reefs grow as far north and south as 35° latitude on the western margins of ocean basins* *Least diversity of reef-building corals in Atlantic ocean.* *Diversity pattern of reef-building coral observed in today's oceans is related to the past positions of the continents.* Reef lagoon habitat

Lost city

*Emits fluids at a much lower temperature/greater pH compared to typical black smokers.* *Builds chimneys of calcium carbonate, instead of the metal sulfides found at typical black smokers.* *Releases methane and hydrogen into the surrounding water instead of hydrogen sulfide and dissolved metals from typical black smokers.* *Thought to be driven by serpentinization.*

Hydrothermal Vent Communities

*Primary producers in hydrothermal vent communities are sulfur-oxidizing archea.* *Biocommunities at active hydrothermal vents had up to one thousand times more biomass than the rest of the deepocean floor.* *Animals found: Mussels, clams, white crabs, tube worm.* *Microscopic archea: most important members.* *Tubeworms and giant clams depend entirely on sulfur-oxidizing archaea that live symbiotically within their tissues Vents active for years or decades* Animal species similar at widely separated vents Larvae drift from site to site "Dead whale hypothesis" Large carcasses may be stepping stone for larvae Life span: - Vents controlled by sporadic volcanic activity - Vent may be active for only years to decades - Organisms die when vent is inactive - Increased volcanic activity can kill organisms

Crown of thorns phenomenon

*Sea star destroys coral reefs by eating coral polyps.* Outbreaks (greatly increased numbers) decimate reef Problem in Pacific since 1962 May be part of long-term cycle

Bleached coral

*The loss of color (coral bleaching) in coral reef organisms can be a result of loss of zoocanthellae.* *Coral bleaching often occurs in response to elevated temperatures.*

Crabs

Found at Pacific vent sites Top predators - worms, clams, mussels and archea mats

Zooxanthellae

*Zooxanthellae are autotrophic marine protists that are found in the living tissues of some simple marine invertebrates such as corals, sea anemones, and jellyfish. *Zooxanthellae are dinoflagellates.* *Relationship between the protistan zooxanthellae and the polyps of reef-building corals is best described as a/an mutualistic symbols.* *Most reef-building corals receive about 90% of their nutrition from symbiotic zooxanthellae algae.*

Hydrothermal fluid

- Hot - Acidic (pH 3-4) - Variation in salinity - one third to twice the concentration of normal seawater. - High concentration of dissolved hydrogen sulfide and heavy metals (cadmium, arsenic, lead, cupper). - Highly toxic

Coral reefs

- Reefs: shallow water communities restricted to tropics - Polyps: individual corals. *Does not need strong sunlight.* *Coral reef tourism provides some countries with over 50% of their gross national product.*

Benthic habitats

- Rocky shore (hard bottom, high energy) - Sandy or muddy shore/sediment-covered shores (soft bottom, low energy) - Shallow Ocean floor - Coral reefs - Deep sea floor - Hydrothermal vent

Challenges of living in intertidal zone

1. *Limited space (most important limiting factor)*: - *Larval forms are an adaptation to cope with lack of space or attachment sites.* - Overtake other organisms' space by attaching/living on them. 2. Easy victims for terrestrial predators at low tide: - *Ability to break off body parts and regrow them later is an adaptation to cope with predators.* - *Stinging cells, camouflage, and an inking response are adaptations to cope with predators.* 3. Difficulty finding mates for reproduction: - *Release of large numbers of eggs into the water column is an adaptation to cope with difficulty finding mates.* - *Sea urchins feed directly on living kelp.* 4. Wide daily swings in environmental conditions (temp., salinity, pH, O2: - *Strong attachment threads, biological adhesives, a muscular foot, multiple legs, or hundreds of tube feet are adaptations to cope with strong wave activity*

Coral reefs decline

30% healthy today, down from 41% healthy in 2000 One third of corals - high risk of extinction *Humans: greatest threat. - Overfishing: resulted in algae smothering the reefs. - Acidification: makes it more difficult for corals to build skeletons. - Sea level rise: reduces the amount of sunlight they receive* Other threats - Hurricanes - Global warming - Floods - Tsunami - Disease *Sewage discharge and fertilizer runoff is detrimental to coral growth because it increases the amount of inorganic nutrients in the water that stimulates excessive algal growth.* *Boating, fishing, scuba, snorkeling, and suspended sediment might contribute to the decline of a coral community.*

Cnidaria

Class Anthozoa - *Anemones: protects itself with stinging needlelike cells called nematocysts.* - corals Class Scyphozoa (jellyfish) Class Cubozoa (box jellies) Class Hydrozoa (Portuguese Man o' War)

Symbiosis of coral and algae

Coral reefs made of algae, mollusks, foraminifers as well as corals *Coral reefs contain about three times as much algal biomass as animal biomass. Hermatypic coral - mutualistic relationship with algae - Algae provide food - Corals provide nutrients

Types of vent

Determined by water temperature; Black smokers: - temperature above 350°C - water is black due to the release of metal sulfides (iron, nickel, copper and zinc) White smokers: - temperature between 30° and 350°C - water is white due to the release of light colored compounds (barium sulfide and calcium sulfate) Warm-water vents: - temperature below 30°C - water is clear

Intertidal donation of rocky shore

Epifauna. 1. Spray zone (supra tidal) - void drying out - Many animals have shells - Few species of marine algae - *Periwinkle snail* 2. High tide zone - Avoid drying out - Animals have shells - Rock weeds with thick cell walls - *Buckshot barnacles and limpets* 3. Middle tide zone - More types of marine algae - Soft-bodied animals - *goose-necked barnacles and mussels* 4. Low tide zone - Abundant algae - Many animals hidden by seaweed and sea grass - Crabs, sea stars, sea cucumbers, sponges - *Dominated by red and brown algae and surf grasses.* - *Kelp* *Rock weed are among the first organisms to colonize a rocky shore* *Some organisms living in the high water portion of the intertidal zone cannot survive in the supralittoral zone because they have planktonic larval forms.*

Hydrothermal vents

Geysers on the sea floor where hot water exits into the water column. Located near mid-ocean ridges, transform faults, subduction zones, and hot spots.

Deep sea floor

Least known habitats. *Mud like clay deposits are found on the abyssal plains and in deep trenches.* *Oozes made of dead planktonic organisms are found on the flanks of oceanic ridges and rises.* *Coarse sediments from nearby land sources are found on the continental rise.* Main characteristics: - About the same temperature (2◦C) - About the same salinity (35 g/L) - Oxygen content relatively high - Little to no sunlight - Pressure can be enormous (200-1000 atm) - Food supply is very low Should limit benthic biomass, but there is large diversity of species (small infaunal deposit feeders). They adapt to detect food.

Did life originate at hydrothermal vents?

Life is thought to have begun in the ocean. Vents present during Earth's early history Conditions are uniform and vents provide a lot of energy. Presence of Archaea support the idea due to their ancient genetic make-up. First cells made of organic molecules synthesized from reduced gases (e.g. methane, hydrogen sulfide) supplied by hydrothermal vents.

Distribution of benthic organisms

Mainly on continental shelves to shelf break. *Related to high primary productivity.* *The distribution of benthic biomass closely matches the distribution of chlorophyll.*

Mud flats

Sediment-covered shores; *Represents the lowest-energy environment; Has the lowest species diversity.* *Best developed on a steeply sloping, coarse sand beach.* Organic-rich environment Dominant organisms - Eelgrass and turtle grass common - Bivalves and other mollusks - Fiddler crabs, worms

Sandy beaches

Sediment-covered shores; Animals typically burrow and may move in and out of burrows. *The most successful adaptation for living on a sediment-covered shore is burrowing into the sediment.* Major Groups - *Bivalve mollusks: The depth to which a bivalve can bury itself depends on the length of its siphon.* - Annelid worms - Crustaceans - Echinoderms *The common annelid found in a sandy beach environment is the lungworm.*

Kelp forests

Shallow offshore ocean floor; beds of giant brown bladder kelp and bull kelp that are fast growing, have highly productive ecosystems, and provide shelter for variety of organisms. *Under ideal conditions, the giant brown bladder kelp can grow up to two feet per day.* *The giant brown bladder kelp the fastest-growing Algae in the world.*

Food sources in deep seafloor

The abyssal benthic food chains depend upon food from the surface that reaches the bottom (low). 3% of the organic matter produce in the upper zone of water column.