Comparative Limnology of Inner Long Point Bay, Lake Erie, and Adjacent Waters of the Outer Bay

Environmental characteristics of Inner Long Point Bay and adjacent waters of the Outer Bay were observed from April to November 1978–79, to determine differences in water quality between the two areas and to evaluate long term changes in water quality since the last Inner Bay study in 1962. The Inner Bay is shallow, receives diffuse-source nutrient loadings and supports dense stands of aquatic vegetation. Means of all fourteen parameters measured except nitrate nitrogen, total alkalinity, and dissolved oxygen were significantly different in the two bays. Moreover, seasonal distributions of concentrations of nitrate nitrogen and total alkalinity differed in the two basins due to photosynthetic activity of the macrophytes. Only phosphorus and dissolved oxygen showed similar seasonal patterns in mean concentrations in both bays. The Inner Bay warms more rapidly in the spring, attains higher summer temperatures, and cools more quickly in the autumn. On the basis of total phosphorus concentrations and chlorophyll a standing crops the Inner Bay is eutrophic and the Outer Bay mesotrophic. Apparent changes in the Inner Bay environment since 1962 include increases in nitrate and nitrite nitrogen and total alkalinity. Differences in nitrate concentrations between the two studies are probably due to changes in agricultural practices in the drainage basin. Changes in the seasonal cycle of total alkalinity indicate greater photosynthesis by macrophytes during the recent study. The data suggest continuation of a gradual enrichment process in the Inner Bay.