M. Munawar

The seasonality of phytoplankton in the North American Great Lakes, a comparative synthesis

The phytoplankton and productivity of the North American Great Lakes has been studied extensively by Fisheries and Oceans Canada during the past 15 years to monitor the impact of nutrient and contaminant loading on the plankton of the ecosystem. Lakewide cruises were conducted at monthly intervals mainly during the spring to fall period. This provided extensive biomass, species, size, productivity and nutrient concentration data for the Great Lakes. These data were collected using the Utermöhl inverted microscope technique together with standardized taxonomic, productivity and data-handling procedures. These standardized methodologies were applied to all the Great Lakes which resulted in a comprehensive phycological and ecological data base for the first time. These data form the basis for the evaluation of the complex phenomenon of seasonality.The eutrophic/mesotrophic Lower Great Lakes exhibited well-developed seasonal peaks of high biomass, with inshore-offshore differentiation and spring maxima most pronounced in the inshore region. However, the oligotrophic Upper Great Lakes had low biomass and generally lacked well-developed seasonal patterns. No marked seasonal trends were observed in the ultra-oligotrophic Lake Superior. The seasonality of biomass and various taxonomic groups of phytoplankton showed differentiation between individual lakes and is discussed in detail. The seasonal succession of species provided interesting comparisons between the Lower Great Lakes, which harbour eutrophic and mesotrophic species, and the Upper Great Lakes, which harbour oligotrophic species.Due to the voluminous nature of our data, a general overview has been given for all the Great Lakes with Lake Ontario treated in detail as a case study. The Lake Ontario case study provides the state-of-the-art status ranging from the lakewide surveys of 1970 to the current research with minute organisms such as ultraplankton and picoplankton.

Limnological studies on freshwater ponds of Hyderabad — India

Seasonal abundance of phytoplankton has been discussed in three tropical ponds of Hyderabad, India during two years of investigation. The observed patterns have been characterized as seasonal maxima and minima during summer, monsoon and winter. The tropical patterns observed in the study ponds were typical but different from those observed in temperate regions. Most of the maxima were observed in winter and the minima during the monsoon or rainy season. Diatomeae dominated the phytoplankton of all the ponds in all seasons. An inverse relationship between Diatomeae and Cyanophyta, and Diatomeae and Euglenineae was observed. The phytoplankters have been grouped as perennial, summer, monsoon and winter species.

Is the ‘microbial loop’ an early warning indicator of anthropogenic stress?

Various components of the ‘Microbial loop’ such as bacteria, heterotrophic nanoflagellates and autotrophic picoplankton were analyzed, for the first time across the Great Lakes, during a cruise in the summer of 1988. In addition, the size fractionated primary productivity using carbon-14 techniques was also determined. The statistical analysis indicated that bacteria, autotrophic picoplankton and ultraplankton/picoplankton productivity were significantly higher in Lakes Ontario and Erie than Lakes Huron and Michigan. The autotrophic picoplankton and ultraplankton/picoplankton productivity was higher in Lake Erie compared to Lake Ontario.The autotrophic picoplankton showed sensitivity to nutrients and contaminants in various types of environments. A dramatic decrease of autotrophic picoplankton in eutrophic-contaminated areas, such as Ashbridges Bay, Hamilton Harbour and western Lake Erie was observed. Conversely, in Saginaw Bay, another eutrophic environment, the autotrophic picoplankton were significantly higher than in Lake Huron. The sensitivity of autotrophic picoplankton to nutrients/contaminants might have implications to trophic interactions. Our results suggest that structural and functional characteristics of the ‘microbial loop’ may be operating differently in stressed versus unstressed ecosystems. The possibility of using autotrophic picoplankton as an early warning indicator of environmental perturbation is proposed.

Protecting and managing the Arabian Gulf: Past, present and future

The Arabian Gulf (also known as Persian Gulf and ROPME Sea) represents an extremely important economic, political and strategic aquatic resource. Although the Gulf region is known world wide for its oil-gas deposits and production, very little is known about its ecosystem health, food web dynamics, fisheries, biodiversity and sustainability. The present study reviews and highlights the major anthropogenic stressors which threaten the marine and coastal ecosystems of the Gulf. The Arabian Gulf environment lacks the holistic, ecosystem-based research and monitoring that have been conducted in other marine ecosystems. There is a need for multi-disciplinary, multi-trophic and multi-agency international investigations including the application of emerging technology. Such an integrated strategy is urgently needed to save the rapidly changing marine ecosystems from the impact of rapid and vigorous coastal development across the entire Gulf region. The necessity of developing and implementing ecosystem health agreements between the various riparian countries is emphasized for expeditious protection, conservation and management of this precious but threatened natural heritage.

The Impact of Sediment-Associated Contaminants from the Niagara River Mouth on Various Size Assemblages of Phytoplankton

The impact of elutriated sediment-associated contaminants from the Niagara River mouth and from a midlake station in Lake Ontario on various size assemblages of natural phytoplankton was determined. The C14 fractionation bioassays indicated that the addition of Chelex-treated elutriate (without dissolved metals) from the Niagara River mouth enhanced the C14 uptake when compared to the standard elutriate. Conversely, at the midlake station, the addition of standard elutriate (with dissolved metals) induced higher C14 uptake than the Chelex-treated elutriate. It is apparent that the synergistic effects of nutrients/metals and metals/organic compounds determine the bioavailability and toxicity of contaminants to natural phytoplankton. Our technique is sensitive and useful in detecting the differential response of algal size fractions to contaminants.

Limnological studies on freshwater ponds of hyderabad-India: II. The Biocenose Distribution of unicellular and colonial phytoplankton in polluted and unpolluted environments

SummaryThe paper is based on a two-year study of the distribution of phytoplankton in three freshwater, polluted and unpolluted ponds of Hyderabad, India. The distribution of several groups of algae likeVolvocales, Chlorococcales, Desmids, Diatoms, Dinoflagellates, blue-greens andEuglenineae exhibited interesting relationships to the physioo-chemical complexes of the ponds, and throws much light on the algal distribution in Indian waters. The discussion revolves around the yearly and overall averages of the ecological factors and the various groups of algae. Dissolved oxygen, oxidizable organic matter, free carbon dioxide, nitrates, phosphates, calcium and sulfides have been found to play a significant role. The fluctuations of certain ratios such as N : P : K, C/N, percent sodium, percent Cl + NO3 and Pearsalls basic ratio

Lake Superior Basin and its Development

\left( {\frac{{{\rm{Na + K}}}}{{{\rm{Ca + Mg}}}}} \right)

The regulation of phytoplankton population dynamics in the world's largest lakes

suggest distinctly important clues in the distribution of various groups of algae.