Biomass and Distribution of Cladophora Glomerata in Relation to Some Physical-Chemical Variables at Two Sites in Lake Erie

Abstract

Cladophora was collected from 0.25-m 2 quadrats on alternate weeks at two sites located in Lake Erie near Hamburg, New York, and Walnut Creek near Erie, Pennsylvania, between June and November 1979. Cladophora biomass and internal nutrients (total Kjeldahl nitrogen and total phosphorus) were determined. Water samples were analyzed for total phosphorus, soluble reactive phosphorus, nitrate + nitrite nitrogen, total Kjeldahl nitrogen, and ammonia nitrogen. Temperature and Secchi disk transparency were also recorded. The peak standing crop for Cladophora was 211 gDW/m 2 (July) at the Hamburg site and 57 gDW/m 2 (July) at Walnut Creek. The depth distribution of Cladophora at the sample sites was influenced by wave activity and drifting sand. As a result of sand scouring at the shallower depths, Cladophora biomass generally was greatest at the 3-m depth. Reductions in Cladophora internal nutrients corresponded to decreased nutrients in the water. Cladophora detached from its substrate during periods when low internal nutrient levels were observed. Internal total phosphorus concentrations were low and approached the minimum cell quota (0.05–0.06% –P) most of the time. Soluble reactive phosphorus values were also low (1–4 μgP/L). Levels of soluble reactive phosphorus and internal total phosphorus were low and almost always limiting, and may be responsible for the low biomass values observed. In addition, internal total phosphorus levels showed a significant positive correlation with Cladophora biomass. Internal total nitrogen values were generally less than 1%-N at Walnut Creek and ammonia nitrogen measurements were near detection limits. Cladophora was nitrogen-limited at the Walnut Creek site during part of the study period. Nitrate + nitrite nitrogen showed a significant positive correlation with Cladophora biomass at that site.