166 
Nutients—may limit or enhance plant growth. Nitrogen and 
phosphorus are especially important. 
Salinity—varies with season and tide. Tolerance varies with species. 
Salinities less than seawater characteristic of estuaries. Extremes 
are lethal to estuarine organisms. Variations are important. 
Temperature—varies with season and tide. Tolerance varies with 
species. Variations are important to some species. 
Transparency—clearness of water, may limit vertical extent of 
plant growth. 
Estuarine form 
Shape—influences circulation, number and size of habitats available. 
Size—influences circulation, area available for productivity, 
habitats. 
Character of bottom and topography—influences circulation, deter- 
mines suitability for benthic habitats. 
LAND USE—HESTUARINE INTERACTION 
The survival of estuarine species depends on the stuarine parameters 
listed above. Land uses which affect these parameters will alter the 
ecological balance and may reduce the value of the estuarine area. 
Important effects may range from changing the absolute levels of 
of certain parameters to increasing or decreasing the variations of 
these parameters. The specific effect that a change will have on the 
biology of an estuary cannot be generally determined. However, 
once the interaction is identified, research can be initiated to de- 
termine the extent and significance of the effect. It is important to 
know whether an interaction will occur, and through what mechanism. 
Table II summarizes various land uses and their effects on the 
estuarine environment. The primary influence is marked with a 
(1), secondary effects are marked with a (2). An (s) under form in- 
dicates that the change results primarily from sedimentation. 
TABLE II.—LAND USE—EFFECTS ON ESTUARINE PARAMETERS 
Activity and location Flow. Water Form 
Watershed activity: 
Damconstwuction. 2.2. Pee ae, Sue ee ee 1 2) de PON 
Streamflow augmentation._._______________________- eee, ee 1 2 2s) 
‘Land use: 
VASTICUILUTC Seem ek =o =< Ae ie 2 s SeeRea eeeos nere ee 1 1 2(s) 
AUTTeL UST eae «ame Me "ai ce gh OP ty ty eS Se eee ae Se 
Urbain? 2249: ee ae eek Eee PIE IO ae IL} etd b 2” 2(s) 
‘Power generation (heat discharge)______________________________-_-=----+=----- Vs eens 
NTT ea a NE ie hn a ee ae ec 1 2(s) 
Heavy construction, roads_-_____________________-____ ee Deen ath Ss PEO 2(s) 
lEstuarine activity: 
‘Marine construction ereaniaers: barriers) I OES i | 1 2 2(s) 
iLand use: 
NBRiCUILU Tal eee Sere ees LON ke ee ae ee SS 1 1 2(s) 
TRCUS trial: Se ee eee See I ele Rt penne ee sae Le...) a ee 
(BF) eae i a es A oh al A MN ALD pl Sent ted Pes gn. 2 2(s) 
‘Power generation (heat discharge)__________________________________---------- pissy Se eRe 
Marre File es Be ee ea Sete EP ADEL oS SMR D1 Nee eee 1 
Transportation: 
Dredeing (if required) 25. aes ee a Soc De le ee ee 1 
Pollutionshazard2es C25 SEL eee hs ee ee Nie aaa UGS eee 
Mining: 
Sediment-sa ne. i Ses Sere es eae eee | oo Se a 1 VAD BCCI SE RR TEESE 1 
