| Abstract: | Abstract Intermittently open/closed coastal lakes and lagoons are susceptible to contamination and nutrient‐enrichment. Although many of them are considered to be degraded, our understanding of their ecology and the effects of anthropogenic activity is limited. This study of coastal lakes in New South Wales compared the density and distribution of macrobenthos in localities that differed in their degree of isolation from the sea, that is, open versus closed lakes and mouths versus inner reaches. Lakes kept open artificially (to improve water quality and reduce flooding), were also compared with naturally open or closed lakes. Densities of macrobenthos were usually greater in the mouths of open than of closed lakes, but the opposite was true in inner reaches. While isolated localities differed more between lakes than did mouths, small‐scale variability was greater in the latter. Spatial patterns were less temporally consistent in inner reaches than in mouths. Differences in densities and spatial variability between mouths and inner reaches were influenced primarily by whether a lake was open or closed and secondarily by manipulation of the mouth. While, for example, densities in open manipulated systems were usually greater in the mouths, but smaller in the inner reaches, the effect of manipulation was less obvious in closed lakes. Differences in density between types of lakes were not clearly related to physical factors although, within lakes, benthos generally correlated negatively with salinity and positively with median particle‐size, silt and organic content. The effects of factors that modify the degree of isolation of coastal lakes are discussed and it is concluded that current levels of isolation do not appear to affect macrobenthos adversely. Nevertheless, increased isolation, which is likely as a result of climatic change, may well do so, particularly in lakes already stressed by human impacts. |
