Atmospheric pressure . Atmospheric "highs" and "lows" cause temporary 

 changes in sea level and may temporarily affect the circulation by bringing 

 dynamic forces into action. 



The most extreme deviations on the Maine coast occur during extratropical 

 cyclones producing "northeasters" and tropical cyclones producing "tropical 

 storms" and "hurricanes." Coastal flooding and habitat destruction and/or 

 alteration are often associated with these storms or low pressure systems. 

 Mass mortalities of animals and "uprooting" of macroalgae may occur. The 

 flushing action associated with flooding is particularly important in 

 redistributing detritus from the high intertidal (emergent wetlands and wrack 

 area) and terrestrial systems into the marine system. Flooding may also 

 distribute pollutants (e.g., oil) into the high intertidal zone, where 

 emergent wetlands and wrack communities may be impacted. 



Storms affect the stability of the thermocline. Sufficiently severe storms 

 can generate enough turbulent energy to cause some mixing across the 

 thermocline. The energy of storm-induced mixing declines more or less 

 exponentially with depth. Storms are also often a factor in influencing the 

 timing of the fall overturn of the water column. 



The direction and speed of currents are influenced by storms. The current 

 direction is determined by whether the Storm system passes to the north or 

 south of a given area (see "Processes influencing coastal waters" above) and 

 current speed is related to the intensity of the winds associated with the 

 storm. 



Ice formation . Ice formation may have major effects on biota, including 

 marine invertebrates and waterbirds. Ice forms along the shore in protected 

 areas (mostly estuarine) for varying lengths of time each winter. Ice 

 movement may dislodge individuals. In extreme conditions the water may freeze 

 all the way to the bottom and suffocate all the biota. During years of 

 extensive ice formation, large areas of substrate, including biota, may be 

 transported in ice rafts. 



The freezing of mudflats may affect waterbirds, who traditionally "home" to 

 specific flats in winter for feeding. Long periods of icing may result in the 

 starvation of these species. Where tidal fluctuations are greatest (in 

 eastern Maine; especially Cobscook Bay, region 6) icing is less likely to 

 occur. 



Additional information on climatic parameters is found in "Climate", page 

 2-9 in chapter 2. 



BIOTIC FEATURES 



Within the environment created by the abiotic features lives the biota of the 

 marine ecosystem. It is divided by function into three interrelated groups: 

 the producers, the consumers, and the decomposers. 



Producers 



Producers construct new organic material from inorganic matter. In the marine 

 environment the major producers include the macroalgae, rooted macrophytes, 



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