Lecture 19 BENTHIC ORGANISMS Chapters 13 16 DISTRIBUTION

Lecture 19: BENTHIC ORGANISMS Chapters 13 -16

DISTRIBUTION OF BENTHIC ORGANISMS • More benthos beneath areas of high primary productivity • Mainly on continental shelves to shelf break • Affected by surface ocean currents

FEEDING STRATEGIES • Suspension feeding or filter feeding – Take in seawater and filter out usable organic matter • Deposit feeding – Take in detritus and sediment and extract usable organic matter • Carnivorous feeding – Organisms capture and eat other animals

FEEDING STRATEGIES Suspension feeding Deposit feeding Carnivorous feeding

SUSPENSION FEEDERS • Filter water for edible particles • Water and food swept in by movement of cilia on gills • Food settles on gills, driven towards mouth and swallowed Fig. 15. 13

BENTHIC ORGANISMS ON ROCKY SHORES • Epifauna – Attached to substrate (e. g. , marine algae) – Move over seafloor (e. g. , crabs, snails) • Moderate diversity of species – Greatest animal diversity at tropical latitudes – Greatest algae diversity at mid-latitudes (more nutrients)

ROCKY SHORE ZONATION (INTERTIDAL ZONE)

CHALLENGES OF LIVING IN THE INTERTIDAL ZONE 1. Drying out at low tide = desiccation • seek shelter • thick exoskeleton or shell 2. Potentially strong wave action – damaged or swept away • strong attachment – biochemical “glues” or mechanical grasping • hard structures 3. Easy victims for terrestrial predators at low tide • firm attachment • stinging cells • camouflage • inking • expendable parts that can regenerate

CHALLENGES OF LIVING IN THE INTERTIDAL ZONE 4. Reproduction – can’t find mate if attached • external fertilization – broadcast reproduction • extendable organ to reach others 5. Wide daily swings in environmental conditions (temp. , salinity, p. H, O 2) • withdraw into protective shell • physiological adaptation to conditions 6. Limited space • overtake other organisms’ space • attach to other organisms and live on them

INTERTIDAL ZONATION (ROCKY SHORE) • Spray zone (supratidal) – Avoid drying out – Many animals have shells – Few species of marine algae Periwinkles

INTERTIDAL ZONATION (ROCKY SHORE) • High tide zone – Avoid drying out so animals have shells – Marine algae—rock weeds with thick cell walls • Middle tide zone – More types of marine algae – Soft-bodied animals • Low tide zone – Abundant algae – Many animals hidden by sea weed and sea grass – Crabs abundant in all intertidal zones

BENTHIC ORGANISMS ON SEDIMENT COVERED SHORES Similar intertidal zones Less species diversity Greater number of organisms Mostly infauna – Burrow into sediment • Microbial communities • •

BENTHIC ORGANISMS ON SEDIMENT COVERED SHORES • Examples of types – Coarse boulder beaches – Sand beaches – Salt marshes – Mud flats • Energy level along shore depends on – Wave strength – exposed or protected from open swell – Longshore current strength – Beach slope • Fine-grained, flat-lying tidal flat more stable than high energy sandy beach

INTERTIDAL ZONATION (SANDY SHORE)

SANDY BEACHES • Animals typically burrow and may move in and out of burrows • Major Groups – – Bivalve mollusks Annelid worms Crustaceans Echinoderms

MUD FLATS • Exposed at low tide • Organic-rich environment • Dominant organisms – Eelgrass and turtle grass common – Bivalves and other mollusks – Fiddler crabs

SHALLOW OCEAN FLOOR • Continental shelf • Mostly sediment covered – similar to mudflats • Rocky seafloor - Kelp forests in relatively clear water – urchins – sea otter – lobsters – oysters

BENTHIC ORGANISMS OF THE DEEP • • Least known habitat Little to no sunlight About the same temperature About the same salinity Oxygen content relatively high Food supply is very low Pressure can be enormous Bottom currents usually slow

FOOD SUPPLY TO THE DEEP • Most food from surface waters • Low supply

seafloor seems devoid of life Time sequence of attack on newly fallen fish by benthos foragers quickly flock to food fish almost completely devoured