Phytoplankton are microscopic marine plants floating near or on the surface of the water. They contain chlorophyll and are dependent on sunlight in order to live and grow, which is why most phytoplankton can be found floating on the upper part of the ocean where sunlight is plentiful. Besides sunlight, they also need carbon, which they get from carbon dioxide (CO
) because these phototrophs are also autotrophs, as well as nitrogen, phosphate and sulfur, which they will convert into proteins, fats, and carbohydrates. Jellyfish, shrimp and whales are some of the marine animals that will feed on phytoplankton.
Diatoms capture the energy from the sun during photosynthesis and convert this energy into carbohydrates that will be passed on to other marine life as food or an energy source. Many of the ocean's herbivores feed on phytoplankton. Phytoplankton produce oxygen so that other species in the water and on land can survive, including humans. However, an excess of phytoplankton can pose serious health risks. Dinoflagellates, a red phytoplankton, causes "red tides" that are toxic. Clams will eat the dinoflagella toxins, causing a health risk to those that eat these clams. Even an excess of non-toxic algae can cause lethal hypoxic or low oxygen levels in the water. The dead and dying algae, as they decompose, use up massive amounts of dissolved oxygen causing the oxygen levels in the water to drop dramatically, which can become dangerous to other marine organisms.
All types of algae contain chlorophyll allowing them to be able to make their own food through photosynthesis and CO
fixation. Plants are autotrophs because they make their own food, sugar or cellulose, by fixing or capturing the CO
from the atmosphere during photosynthesis. There must be chlorophyll, sunlight and carbon dioxide in order for photosynthesis and CO
fixation to transpire. Algae also require water and other nutrients for their survival. In the presence of all these components, algae will flourish, rapidly reproducing in large numbers. This sudden outburst in algal growth is called an algal bloom. These blooms occur as waste, which contains the nutrients algae need in order to reproduce quickly, is dumped into the water. Algal blooms can be extremely harmful to the other organisms living in the water. Bacteria will use the oxygen in the water to break down the dead algae. When the bacteria use too much, the other organisms do not have enough oxygen to survive and will die.
Brown algae is macroalgae or seaweed or kelp as it is more commonly known, and can be found floating near the surface of the water. Brown algae are the largest of all the algae as it flourishes. Organisms eat seaweed and also use the seaweed to protect themselves from predators. Different types of seaweed are distinguishable by their pigments: red, brown and green. In the tightly packed beds of the brown alga kelp, small fish and invertebrates are found to protect themselves from predators. The green algae are eaten by finfish and invertebrates.
Eelgrass is a vascular plant or true plant that can be found in shallow water. The Eelgrass blades are thin in order for small finfish and shellfish to protect themselves from predators. Eelgrass beds are essential for bay scallops to survive. During the first weeks of their lives the baby scallops attach themselves to the blades to protect themselves as they grow.
Vascular plants such as Spartina are more commonly found in the salt marshes of Long Island Sound. These plants can tolerate tremendously high amounts of salinity. The two most important vascular plants that grow in the marshes are the saltwater cordgrass and the saltmeadow grass. These plants are important both alive and dead. The dead parts of the plant are a source of food for fiddler crabs, worms, snails, and other marine life. Bacteria will continue to break down the plants further, releasing nutrients into the water.