Jacob John

The use of diatoms in monitoring the development of created wetlands at a sandmining site in Western Australia

Former sand-mining pits at Capel, 200 km south of Perth in Western Australia, have been rehabilitated into artificial wetlands since 1975–1979. A chain of fresh water lakes was created as a potential waterbird refuge and an area for passive recreation. Initially, the lakes had low pH, high ammonium, iron and manganese levels and low phosphorus concentration. The lakes were characterised by low diversity of diatoms dominated by acidophilous species. Following an increase in pH in the effluent water discharged into the lake from the mining process plant and landscaping of the lakes since 1988, the diversity of diatoms gradually increased. The system is now dominated by periphytic diatom communities, preferring high conductivity. There has been a marked transition in the diatom community from acidophilous to alkaliphilous species. Planktonic diatom blooms replaced dinoflagellate blooms. Concomitantly, there has been a dramatic increase in the diversity of invertebrates and waterbirds in these lakes. The value of diatoms in assessing the progressive development of created wetlands as self-sustaining ecosystems at sand mines in Australia is discussed.

Climaconeis stromatolitis, a new species of diatom from Shark bay, Western Australia

The structure, morphology and ecology of Climaconeis stromatolitis a new species of diatom associated with living stromatolites in Shark Bay, Western Australia are presented. This species is distinguished from other described species of Climaconeis by the presence of a pair of H-shaped plastids, its strong stauros and fine striae.

CYCLOTELLA CRETICA, A NEW SPECIES OF DIATOM FROM THE ISLAND OF CRETE, GREECE

The morphology, systematics and ecology of a new centric diatom—CycZotelZa cretica, from Lake Kournas in the island of Crete, Greece—are reported. The morphological variation and ultrastructure of the diatom are described as revealed by light and scanning electron microscopy. The species is characterised by a smooth flat central area with one to five, mostly three, central fultoportulae, a marginal zone of striae with several marginal fultoportulae, and a single submarginal rimoportula on the valve face. The morphology of C. cretica is compared with that of other taxa in the genus Cyclotella.

MORPHOLOGY AND ULTRASTRUCTURE OF THE CENTRIC DIATOM CYCLOTELLA DISTINGUENDA

Cyclotella distinguenda Hust. was studied in material from Lake Kournas in the Island of Crete, Greece. It is characterised by a highly variable central area without any processes, a striate zone of varying width with simple alveoli, a single marginal rimoportula. and several marginal fultoportulae. Analyses of the populations reveal two clusters of morphotypes, distinguished by size range and the relative size of the central area, which appears to represent life cycle variation. The affinity of C. distinguenda with other species of Cyclotella is discussed.

MUCILAGE STRUCTURES OF MASTOGLOIA FIMBRIATA AND MASTOGLOIA COCCONEIFORMIS EXAMINED BY THE ENVIRONMENTAL SCANNING ELECTRON MICROSCOPE (ESEM), A NEW TOOL FOR DIATOM STUDIES

The environmental scanning electron microscope (ESEM) is a new tool which enables imaging of specimens in their natural state. The potential of this tool for studies of fresh diatom material, especially delicate structures like extracellular exudates, is illustrated by preliminary results obtained on Mastogloia fimbriata (Brightwell) Cleve and Mastogloia cocconeiformis Gran.

Bioassessment of Health of Aquatic Systems by the Use of Diatoms

Physical and chemical monitoring of water quality has been practiced for a long time. There are standard techniques and guidelines for measuring light penetration, turbidity, conductivity, total dissolved salts, dissolved oxygen, biological oxygen demand, and nutrients: phosphates, nitrates, nitrites, ammonia, and so on (Chapman, 1992). Many regulatory agencies routinely monitor the physical and chemical properties of rivers, streams, and lakes. Measurements of these properties provide us with simple values, determined at a given time, but do not provide an overview of the health of the ecosystems. Water quality and habitats are integral components of an aquatic system. As water resources on regional, national, and international levels are undergoing rapid degradation, assessment of their health is considered urgent (Norris & Norris, 1995). Such assessment will enable us to take preventive as well as restorative measures. This chapter deals with a group of ubiquitous, easily quantifiable organisms as diagnostic tools in assessing aquatic system health—the diatoms.