While tidal currents are extreme and dominate flow, significant residual 

 nontidal flows occur. Chevier (1959) measured these monthly throughout 1957, 

 using drift bottles and radar-tracked drift poles. He concluded that wind 

 speed and direction were very effective in determining the residual flow. 

 Summer winds from the south tend to confine surface waters to Passamaquoddy 

 Bay, while winter northwest winds remove them. Cobscook Bay tended to have an 

 outward residual flow at all times. Monthly drift bottle trajectories are 

 presented in Chevier (1959). 



Forgeron (1959) presents seasonal temperature and salinity data measured at 

 the surface and near bottom at 10 stations within this region. With only rare 

 exceptions, very little difference exists between surface and bottom 

 temperatures and salinities. Maximum temperature differences of 6 °F (2° C) 

 between surface and bottom occurred at the deeper [131 feet (40 m)] stations 

 and maximum differences in salinity of 1 to 3 ppt were found only during high 

 freshwater flow (April or May) . Seasonal water temperatures varied 

 sinusoidally from extreme winter lows of 32 to 36°F (0 to 2°C) to summer highs 

 of 54 to 57°F (12 to 14°C). Comparable salinity variations were small, with 

 maximum variations from 29.5 to 32.5 ppt and a smaller range for many 

 individual stations. These observations reflect the generally oceanic nature 

 of these waters and the extreme vertical mixing in them that results from 

 tides. Tidal variations reflect both tidal excursion and lateral gradients. 

 The tidal excursions are large but lateral gradients are small, so the 

 resultant tidal variations also are small. 



Climate 



Meteorological factors that influence the other abiotic factors (hydrography 

 and geology) as well as the biota are described below. 



Wind. Winds play an important role in moving surface waters (see 

 "Hydrography" above). Their effect depends on strength, duration, and fetch 

 (the extent of their influence) . The predominant winds in coastal Maine are 

 from the southwest in summer and from the northwest in winter (see "Climate," 

 page 2-9 in chapter 2) . Wave action produced by wind provides moisture to the 

 intertidal zone at levels higher than a calm sea provides. This added 

 moisture allows intertidal communities to develop higher in the intertidal 

 zone than they would in protected areas (e.g., inner bays; see "Introduction 

 to the Subtidal and Intertidal Subsystems" below) . Winds associated with 

 storms are discussed below. 



Heat budget and precipitation . Water temperature in estuaries depends on 

 the degree of heat interchange at the air-water interface, the temperature of 

 fresh water inflow, and tidal currents. The level of salinity in an estuary 

 is determined partly by the amount of precipitation and surface evaporation. 



Water temperatures sometimes are critical to the biota, because many plants 

 and animals need a minimal summer temperature to induce reproduction, and if 

 it is not reached in a given year little or no recruitment takes place. Some 

 species in Maine are at the northern edge of their ranges, are scarce, and 

 cannot reproduce because of low temperatures. An example is the quahog, which 

 survives only in small pockets of warm water. Summer water temperatures are 

 lower in the northeastern part of the State (regions 4 to 6) than in the 

 southwestern section (regions 1 to 3; Bousfield and Laubitz 1972), so species 



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