Investigations on phytoplankton with special reference to water usage

Experiments and observations on the phytoplankton of certain lakes in the English Lake District were made from early 1973 to the end of March, 1974. They included laboratory and lake bioassays and observations on the quantity and quality of the phytoplankton in six lakes. The introductory sections of the report are about algae, the ecology of phytoplankton and the scope of the contracted work. Laboratory bioassays on water from one lake, Blelham Tarn, showed that phosphorus, silicon (for diatoms) and organic substances forming complexes with iron were the major substances limiting the growth of the algae tested. The growth of the test algae was limited to different degrees by those substances and, to some extent, to a greater or lesser degree at different times of year. It is suggested that a relatively simple form of bioassay could give valuable information to water undertakings. Lake bioassays and other experiments were carried out by using large in situ tubular plastic enclosures. Two such investigations are described. The effects of a change in sewerage in two drainage basins on the phytoplankton of three lakes is described and some data given about changes since 1945 in three other lakes in the same overall drainage basin. These latter lakes have been affected too by changes in sewerage and by increasing inputs of domestic and agricultural wastes. Throughout, the relevance of the work done to practical problems of water usage is kept in mind and discussed. In the last section special reference is made to the largely unpredictable results of water transfers. The report ends with a note on river phytoplankton.

Catch rates and demographics of loggerhead sea turtles (Caretta caretta) captured from the Charleston, South Carolina, shipping channel during the period of mandatory use of turtle excluder devices (TEDs)

Trawling was conducted in the Charleston, South Carolina, shipping channel between May and August during 2004–07 to evaluate loggerhead sea turtle (Caretta caretta) catch rates and demographic distributions. Two hundred and twenty individual loggerheads were captured in 432 trawling events during eight sampling periods lasting 2–10 days each. Catch was analyzed by using a generalized linear model. Data were fitted to a negative binomial distribution with the log of standardized sampling effort (i.e., an hour of sampling with a net head rope length standardized to 30.5 m) for each event treated as an offset term. Among 21 variables, factors, and interactions, five terms were significant in the final model, which accounted for 45% of model deviance. Highly significant differences in catch were noted among sampling periods and sampling locations within the channel, with greatest catch furthest seaward consistent with historical observations. Loggerhead sea turtle catch rates in 2004–07 were greater than in 1991–92 when mandatory use of turtle excluder devices was beginning to be phased in. Concurrent with increased catch rates, loggerheads captured in 2004–07 were larger than in 1991–92. Eighty-five percent of loggerheads captured were ≤75.0 cm straight-line carapace length (nuchal notch to tip of carapace) and there was a 3.9:1 female-to-male bias, consistent with limited data for this location two decades earlier. Only juvenile loggerheads ≤75.0 cm possessed haplotypes other than CC-A01 or CC-A02 that dominate in the region. Six rare and one un-described haplotype were predominantly found in June 2004.