Organisms in this area include anemones, barnacles, chitons, crabs, green algae, isopods, limpets, mussels, sea lettuce, sea palms, sea stars, snails, sponges, and whelks. Low Tide Zone: Also called the Lower Littoral Zone.

Intertidal zones of rocky shorelines host sea stars, snails, seaweed, algae, and crabs. Barnacles, mussels, and kelps can survive in this environment by anchoring themselves to the rocks. Barnacles and mussels can also hold seawater in their closed shells to keep from drying out during low tide.

Mussels need a constant supply of water where they can pump large volumes of water that contain food. The higher up in the intertidal zone, the less water is available. The less water means less food. The lower they can live leads to more water and more food.

Littoral zone, marine ecological realm that experiences the effects of tidal and longshore currents and breaking waves to a depth of 5 to 10 metres (16 to 33 feet) below the low-tide level, depending on the intensity of storm waves. The geological nature of shorelines and nearshore bottoms is exceedingly varied.

Bathyal zone, marine ecologic realm extending down from the edge of the continental shelf to the depth at which the water temperature is 4° C (39° F). Both of these limits are variable, but the bathyal zone is generally described as lying between 200 and 2,000 m (660 and 6,600 feet) below the surface.

littoral zone

Shallow lakes are lakes where the sunlight can reach the bottom. Generally, this corresponds to 15 feet deep or less. Since the sunlight can reach the bottom, plants are able to grow there. Deep lakes only mix in spring and fall, and the bottom of deep lakes stays cold and dark because light cannot reach the bottom.

Cloudy or stained water, which limits light penetration, may restrict plant growth. In lakes where water clarity is low all summer, aquatic plants will not grow throughout the littoral zone but will be restricted to shallow areas near shore.

Cold water can hold more dissolved oxygen than warm water. In winter and early spring, when the water temperature is low, the dissolved oxygen concentration is high. In summer and fall, when the water temperature is high, the dissolved-oxygen concentration is often lower.

Ponds or lakes are divided into 3 categories; they are either Oligotrophic, Mesotrophic, or Eutrophic stages of their life (listed youngest to oldest).

A thermocline (sometimes metalimnion in lakes) is a thin but distinct layer in a large body of fluid (e.g. water, such as an ocean or lake, or air, such as an atmosphere) in which temperature changes more rapidly with depth than it does in the layers above or below.

Lake turnover is extremely important in freshwater lakes, as it is the event that is responsible for replenishing dissolved oxygen levels in the deepest lake waters. When the lakes are a uniform temperature and density, it takes relatively little wind energy to mix water deep into the lake.

A lotic ecosystem can be any kind of moving water, such as a run, creek, brook, river, spring, channel or stream. Rapids are the areas where the water is fast enough to keep the bottom clear of materials, while pools are deeper areas of water where the currents are slower and silt builds up.