Producers 



Producers construct new organic material from solar energy and inorganic 

 matter. In the estuarine system, the major producers include the macroalgae, 

 rooted macrophytes, phytoplankton, and benthic diatoms. To an undetermined 

 extent, certain microbes may be involved in the biological production of the 

 estuarine system. The major difference between the production of the marine 

 and estuarine systems is that the productivity of the marine system is 

 dominated by phytoplankton, whereas in estuarine areas productivity is shared 

 by several components, i.e., phytoplankton, macroalgae, benthic diatoms, and 

 rooted aquatic plants. 



Phytoplankton . Phytoplankton is a collective term for the several major 

 groups of microscopic algae that are suspended in the water column. In Maine, 

 diatoms occur most frequently and in the largest numbers. These organisms 

 occur in chains and single cells in bizarre shapes and sizes ranging from 

 about 10 to 100 microns. Their cell wall is composed of silica and they have 

 very low motility. The genus Chaetaceros , along with Skeletonema costatum and 

 Thalassiosira , are dominant diatoms in temperate waters. 



Dinof lagellates , the next most abundant group, are more abundant offshore and 

 in waters south of Maine. They exist mostly as solitary cells; however, some 

 species form chains. Their cell wall is cellulose, and they generally have a 

 flagellum for active swimming. Sizes range from about 3 to 100 microns and 

 the blooms of one species in particular are noted for occurring in swarms 

 known as red tides (see "Red Tide," page 12-31, chapter 12). 



Phytoplankton growth is controlled by estuarine hydrography and climate; 

 specifically, sunlight, nutrients, salinity, temperature, rainfall (and the 

 accompanying river discharge), water transparency, and wind speed and 

 direction. These factors and their interrelationships are discussed with 

 interactions affecting phytoplankton productivity, below. 



Estuarine phytoplankton are grazed upon by animals, including species of 

 zooplankton and fishes. Those not consumed in this way sink to the bottom 

 when they die and either decompose or are consumed by benthic invertebrates. 



Macroalgae and rooted vegetation . Macroalgae, commonly referred to as 

 seaweeds, are the largest forms of algae and are found in great abundance in 

 marine and estuarine areas along the coast of Maine. They range in size from 

 minute plants (e.g., Polysiphonia spp . ) to plants several meters in length, 

 such as the kelps. Seaweeds along rocky coasts form the band of attached, 

 nonrooted vegetation that can be seen between the intertidal zone and shallow 

 waters. Seaweeds are divided into three phyla: the brown algae (Phaeophyta) , 

 the red algae (Rhodophyta) and the green algae (Chlorophyta) . Rooted 

 vegetation include the plants of the emergent wetlands ( Spartina spp. and 

 Juncus spp.) and eelgrass beds ( Zostera marina). 



The brown algae dominate the biomass or bulk weight of rocky shore intertidal 

 and subtidal plant communities. In intertidal rocky shore habitats the brown 

 alga Ascophyllum and various species of Fucus (collectively called fucoids) 

 commonly account for >90% of intertidal plant weight. These plants commonly 

 are known as rockweeds, bladderwrack, or knotted wrack. 



5-40 



