. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0 100 200 300 400 Nitrogen load rate (kg N ha y ) Figure 1. Total number offish per low ± SE (lop panel, left axis) tiinl loinl number of species per low ± SE (lop panel, right axis) are plotted versus nitrogen loading (number ol lish: y = + 23 OV3. r = of species, y = *. + r = ). Median length ol Fundulus heteroclitus and Apeltes quadracus ± SE is plotted versus the total number ol fish per low ± SE (middle left panel). Median length ol Menidia spp. and Fundulus majalis ± SE is plotted
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0 100 200 300 400 Nitrogen load rate (kg N ha y ) Figure 1. Total number offish per low ± SE (lop panel, left axis) tiinl loinl number of species per low ± SE (lop panel, right axis) are plotted versus nitrogen loading (number ol lish: y = + 23 OV3. r = of species, y = *. + r = ). Median length ol Fundulus heteroclitus and Apeltes quadracus ± SE is plotted versus the total number ol fish per low ± SE (middle left panel). Median length ol Menidia spp. and Fundulus majalis ± SE is plotted versus the total number offish per low (middle nghl panel). Regression lines shown for graphs of median length (middle panels) are geometric mean regres- sions (S) (Menidia spp.: y = * + , r = , and F. ma- jalis: y = \ + r = ). The number of planklivorous and bentluvorous fish are slack-plotted versus nitrogen loading (bottom panel). weight regressions for the species collected in our tows. Total biomass of all the species was not related to nitrogen load (re- gression F = : P = ) (data not shown). These results suggest that the fish of Waquoit estuaries are more numerous as nitrogen load increases, hut that the fish in the more enriched estuaries must be smaller. Higher fish densities could result in smaller fish if food supply were limited. To determine whether lengths were reduced where fish were denser, we plotted median length of the four major taxa, Fun- dulus heteroclitus, Fundulus majalis. Menidia spp., and Apt-lies quadracus. versus total density offish (Fig. 1, middle two panels). In two of the four major species (Fig. 1. middle left) length was not related to density, but in the others it was (Fig. I, middle right). F. majalis feeds on bare sand-silt areas (4), which are much reduced in estuaries subject to high nitro- gen loads where macroalgal cover increases (5). Menidia spp. also showed lower size as density increase
Size: 2362px × 1058px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
