The relationships of living things to one another and their environment, or the study of such relationships.
is the study of the distribution, abundance, and relationships of organisms to other organisms and the environment. Ecologists are able to directly observe the diversityDiversity:
The variety of species in a sample, community, or area.
, complexity, and adaptation of living organisms and their habitats through field studies.


Planktonic organisms, like this copepod larva, form the bulk of almost every bivalve's diet.

Most bivalves are filter feeders of phytoplanktonPhytoplankton:
Freely floating photosynthetic organisms in the oceans.
and zooplanktonZooplankton:
Freely floating animals in the oceans, including protozoans, small crustaceans, and the larval stages of larger organisms.
, and have a number of adaptive traitsAdaptive Trait:
A heritable feature of an individual’s phenotype that improves its chances of survival and reproduction in the existing environment.
to maximize their ability to capture food. Most bivalves have cilia on their gills, which capture, sort, and transport food particles. Some have large siphons to allow them to continue feeding while buried in the sand, and others have muscular pumps to take in water and food. Most bivalves filter plankton suspended in the water and are thus called suspension feedersSuspension Feeding:
Feeding type of most bivalves during which organic particles are harvested from the water column.
. Alternatively, some use their siphons or other body parts to disturb the surface of the sediment, then filter the organic material that is stirred up; these are called deposit feedersDeposit Feeding:
Feeding type of some bivalves during which organic particles are harvested (by either the siphons or palps) from the surface or near-surface sediments; see also suspension feeder.
. A few bivalves have symbiotic algae in their tissues that provide energy through photosynthesis or chemosynthesis; another few species are active predators on other animals.

Avoiding Predation

The Cockscomb Oyster (Lopha cristagalli), on a reef in Micronesia, has a jagged shell margin that aids in preventing predation. The shell is naturally deep purple; the red external color here is a coating of living sponge.

Most bivalves, as filter feeders, are low on the food web and have a large number of predators, including starfish, snails, octopus, fish, birds, otters, raccoons, and humans, actively seeking them as a tasty meal. Bivalves have a number of adaptive traitsAdaptive Trait:
A heritable feature of an individual’s phenotype that improves its chances of survival and reproduction in the existing environment.
to help protect them from predators. Most can clamp shut fairly tightly using strong internal muscles. Some bury in the sand to hide, or have thick shells that resist being cracked open, or spines or irregular shell margins to prevent a predator from prying them open.


Mangrove roots are an important habitat for many marine organisms, including bivalves.

Bivalves are a very diverse and adaptive class and have been able to populate most of the Earth's aquatic habitats. Bivalve habitats range from shallow to deep water and include freshwater to estuarine to oceanic environments. Bivalves are also commonly found among seagrass, and mangrove roots, in the mud and sand, and attached to seawalls and rock.

Mode of Life

A fouling community of Zebra Mussels on a current meter from Lake Michigan in 1999.

Mode of life is a general term for how an organism lives. This can include habitat and reproduction, but most often refers to where bivalves are found in their environment. Most bivalves are benthicBenthic:
Occurring at the bottom of a body of water, for example, a seabed, riverbed, or lake bottom.
, that is, live on the sea or lake bottom. Unlike other mollusksMollusk:
A member of the phylum Mollusca; also spelled mollusc (most especially in the United Kingdom).
(such as snails or squid), there are no bivalves that are holoplanktonicHoloplanktonic:
Living as plankton through all stages of a life cycle.
, that is, living their entire life span in the plankton (although most bivalves have planktonic larvae). Benthic lifestyles include infaunalInfaunal:
Living buried within sediment.
(burrowing into the sand), and epifaunalEpifaunal:
Living on top of the sediment, i.e., unburied; also called epibenthic.
(living above the sand, for example, oysters cementing to rock, and mussels attaching to rocks or seagrass blades with byssal threadsByssus:
A tuft of long, tough filaments which are formed in a groove of the foot, and issue from between the valves of certain bivalve mollusks, by which they attach themselves to rocks, etc.
or thin silky fibers). Because of their planktonic larvae, bivalves (especially oysters and mussels) are often important parts of very large fouling communitiesFouling Community:
Community of organisms found attached to hard substrata, most usually human-made, e.g., on the sides of docks, marinas, harbors, or vessels.
on the hard surfaces of boats, seawalls, docks, power plants, etc.


Most bivalves are free-livingFree-living:
Living independently of another organism; not part of a parasitic or symbiotic relationship; or moving independently, i.e., not sessile.
or not directly dependent upon another organism for survival. However, some species depend upon mutual, commensal, or even parasitic relationships with other organisms for survival. For examples, see the How Evolution Works: Coevolution section.