4.2 Key Groups of Marine Organisms

plankton

microscopic free floating marine organism

zooplankton

planktonic consumers that are either floating or weakly swimming animals

echinoderms

a marine invertebrate group with pentaradial symmetry and tube feet

crustaceans

a marine invertebrate group with a hard exoskeleton, ten jointed legs and a nauplius larval stage

bony fish

fish that have a bony skeleton and belong to the class Osteichthyes

cartilaginous fish

fish that have jaws and skeletons made of only cartilage and belong to the class Chondrichthyes

macroalgae

marine producers such as kelp and seaweeds

marine grasses

aquatic flowering plants that are often found in estuarine and coastal environments

keystone species

an organism that plays a unique and crucial role in the way an ecosystem functions; without keystone species the ecosystem would be dramatically different or cease to exist altogether

larvae

a planktonic stage of development which occurs between the egg and juveniles; found in nearly all species of fish and invertebrates

pentaradial symmetry

five arms (or fans) radiating from a central body cavity

tube feet

tubular projections that assist in locomotion, feeding, and respiration

nauplius

A distinct planktonic larval stage seen in many crustaceans.

carapace

the part of the exoskeleton that covers the cephalothorax

gills

the gaseous exchange surfaces of fish

operculum

a thin bony flap of skin covering and protecting the gills

lateral line

a canal on the head and the side of the fish that contains sense organs; it is externally visible in bony fish but in cartilaginous fish it is under the skin

scales

overlapping segments of bone covered by skin and mucus found on the outside of the fish

fins

protrude from the body surface and assist in movement, stabilizing position, reproduction and protection

swim bladder

a buoyancy organ found in bony fish

denticles

a type of overlapping scale that provides protection and improved hydrodynamic efficiency in sharks

gill slits

external openings from the gills through which water taken in at the mouth can pass back to the ocean

holdfast

strong, root-like structure that anchors the macroalgae to the seabed

stipe

long, tough, vertical stalk similar to the stem of plants

blades

leaf-like structures that 'hang' in the water and absorb light and minerals

gas bladder

a gas-containing structure that provides buoyancy for some species of seaweed

root

structure at base of plant that anchors it to the substrate and absorbs nutrients from the nutrients

rhizomes

a horizontal underground structure that enable seagrasses to reproduce asexually

leaf

photosynthetic organ of plants

flower

sexual reproductive organ of plants