A community of living things in a non-living environment that occurs in a specific location where a series of biogeochemical cycles and energy transformations take place is called an Ecosystem. These systems have boundaries that often overlap and are usually devised for the convenience of a particular study of the organisms living there. Ponds, lakes, oceans, forests, estuaries, and grasslands are examples of ecosystems.
Ecosystems are organized into non living, or abiotic, and living, or biotic components. The abiotic components include: sunlight, temperature, precipitation, water, soil and chemical elements and compounds. The biotic components include: primary producers, herbivores, carnivores, omnivores and detritivores. Microbes are usually members of the primary producers or the detritivores. Primary producers, being the organisms that use energy and elements to create biomass that other organisms can feed upon, while detritivores, sometimes called decomposers, are organisms that consume dead organisms returning essential nutrients to the system. Also within these systems are symbiotic relationships between microbes and other organisms (Madigan and Martinko, 6).
Long Island Sound
The ecosystem of Long Island Sound (the Sound) is an estuary consisting of several different habitats. In the Sound, fresh water from rivers and marshes mixes with salt water from the ocean. There are several major rivers flowing into the Sound coming from sources to the north in Massachusetts, Vermont and New Hampshire which provide eighty percent of the fresh water in the Sound. What makes the Sound unique is its two connections to the sea. Where the east side of the sound meets the Atlantic Ocean it is called, "The Race." The West side of the Sound connects to the sea via the East River.
As in most estuaries, a great diversity of plants, animals and microorganisms use the resources in the Sound for food, nesting, breeding, and as a nursery. In 1987 Long Island Sound was designated as a National Estuary (U. S. EPA).
Habitats of Long Island Sound
Within the ecosystem of Long Island Sound there are multiple habitats including: Salt Marshes, Tidal Flats, Rocky Intertidal Zones, Sandy Beaches, the Subtidal Zone, which is beyond the low tide level and constantly submerged, the Benthic Zone, which is the sea floor and the Pelagic Zone, which is the open water area. Plants, animals and other organisms have adapted themselves to survive and thrive in all of these habitats. (Wahle).
Microorganisms in Long Island Sound
Plankton is the most prolific organism in salt water environments. This includes photosynthetic plankton, such as bacteria like Prochlorococcus and algae, called phytoplankton. Phytoplankton play an important role in the survival of all life in Long Island Sound. Because they convert energy form the sun into biomass that is then consumed by other animals, they form the basis of the food chain. Another important function is their ability to convert elemental nutrients such as nitrogen into usable forms making it available to other organisms in the food chain. Also important is their role in the carbon cycle. Through the process of photosynthesis phytoplankton remove CO
2
from the water and release O
2
into the atmosphere. Then, when the phytoplankton die the CO
2
which was converted to carbon as biomass goes to the bottom of the ocean keeping a healthy balance of CO
2
and O
2
in the atmosphere (Hoyle), (enotes.com).
Bacteria can be found in all parts of the water column, on the surface of the sediments and as sediments themselves. Where they live in the water column is dependent on their individual requirements for oxygen or sunlight in the case of photosynthetic primary producers. Aerobic bacteria, because they require oxygen live closer to the surface whereas anaerobic bacteria, that do not require oxygen live in deeper portions of the water column, usually in the sediments below the sediment-water interface. Most water columns contain oxygen throughout except the Black Sea, dead lakes and Long Island Sound during summer hypoxia. Most bacteria in the water column live independently, although some live in symbiotic relationships with other water organisms. For example, bioluminescent bacteria live inside of some jellyfish and can been seen glowing at the surface of the water, of the Sound, near the coast at night (Hoyle).
Sulfate-reducing bacteria are organisms that respire sulfate by releasing hydrogen sulfide (H
2
S) as a waste product. They are dominant microbes in marine systems, such as Long Island Sound, due to the high sulfate content of seawater. The H
2
S is the source of the very distinctive "low tide smell."
Other bacteria in the Sound include anoxygenic phototrophs. These bacteria undergo photosynthesis in which O
2
is not produced. They are also among the first to have
harnessed energy from the sun over 3 billion years ago (Hunter et. al. p.32).
Cyanobacteria are also phototrophs. They are organisms that obtain their energy from light, and are important in Long Island Sound because of their ability to fix nitrogen (see Nutrient Cycles below). They were once called "blue-green algae," although they are not algae--which are eukaryotes more similar to green land plants and found in the Domain Eukarya . In the shallow waters of the Sound, during warm weather months, mats of cyanobacteria can be found. Cyanobacteria are oxygen producing photosynthesizers. These bacteria are also among Earth's earliest phototrophs and were responsible for converting the atmosphere to its present high-oxygen state. (Madigan and Martinko 397-399).