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Eucheuma spinosum is an agar (carrageenin) producing marine alga of commercial value in several countries, including Indonesia. However, its crop yield is often reduced by herbivores. In many areas, herbivores consume almost 100 percent of Eucheuma production. I investigated one way of protecting Eucheuma by application of intercropping of Eucheuma spinosum and Halimeda sp., an unpalatable alga. Laboratory and field experiments were conducted in Indonesian coastal waters. The field experiments were conducted in two areas differing in densities of the main grazer, Syganus, the rabbitfish. In the laboratory Eucheuma was significantly less consumed by Syganus sp. when associated with Halimeda. In the field, I tested two intercropping arrangements: In one, plants of Halimeda and Eucheuma were arranged at 10 cm from each other and in the other they were in direct contact. Results indicate that intercropping with Halimeda reduced density of Syganus and significantly enhanced the production of Eucheuma. At a site where Syganus density was very low, the difference between control and intercropping treatment was not significant. At sites with high Syganus density, the fish consumed all of Eucheuma in controls, while the intercropped plants survived. It is suggested that in habitats where grazing by herbivores causes local extinction, association with Halimeda can present a significant survival strategy for Eucheuma. / Thesis / Master of Science (MSc)

Phytoplankton populations are integral to the structure and function of aquatic ecosystems, and phytoplankton are an excellent study system for exploring ecological questions. Reservoirs often exhibit high horizontal (inflow to dam) and vertical (surface to sediments) environmental heterogeneity, which plays a large role in determining phytoplankton population dynamics. In this thesis, I explore how three bloom-forming phytoplankton taxa, the dinoflagellates Peridinium and Gymnodinium, and the cyanobacterium Planktothrix, respond to horizontal and vertical environmental gradients, respectively. First, I monitored recruitment, or the process of leaving the sediments and entering the pelagic life stage, of dinoflagellates across a horizontal reservoir ecosystem gradient. Surprisingly, coupling of dinoflagellate biology with reservoir physics and chemistry varied along this continuum; recruiting cells were sensitive to reservoir physics (e.g., flow rate, solar radiation) in the upstream riverine zone, while recruitment was related to reservoir chemistry (e.g., dissolved oxygen, nutrients) in the downstream lacustrine zone. This study indicates that upstream habitats should be monitored when studying reservoir phytoplankton dynamics. Next, I investigated the environmental drivers of the vertical distribution and biomass of a hypolimnetic cyanobacterial bloom over two consecutive summers. I collected high-resolution in situ phytoplankton data, and measured environmental variables throughout the water column. Across both years, the vertical distribution of this population was determined by light availability, while the cyanobacterial biomass was predicted by both light and nutrients. These two studies demonstrate that changing physics and chemistry across environmental gradients can regulate phytoplankton dynamics in reservoirs, and phytoplankton monitoring should include more spatially comprehensive sampling approaches. / Master of Science

1- The literature concerning the taxonomy and ecology of soil algae was reviewed extensively. The lack of established, controlled cultural conditions, and the lack of facile isolation techniques in the literature was pointed out. 2- An incubator featuring a controlled environment of 2-40 foot candles of continuous, white, fluorescent light and 25-30 °C was constructed and described. 3- Three composite soil samples were collected and inoculated into cultures of varying chemical and physical characteristics. The primary enrichment cultures thus established were incubated in the incubator at approximately 15 foot candles of light and at 25-30 °C. 4- The mixed algal flora produced in the primary enrichment cultures were separated into unialgal cultures by a technique combining mechanical maceration with bacteriological pour plating. Eighty such unialgal cultures were established. The equipment and the technique were described. 5- Three experiments utilizing small groups of organisms were set up to investigate the general effect of light intensity and agarized media upon algal growth. The results indicated that algal growth is hastened by lighting near the 30 foot candle range and the presence of 0.3-0.7% agar in the medium. 6- The Rhodes centrifuge technique for the staining of protozoa was modified to produce a rapid staining schedule for soil algae. This schedule involves killing and fixing in “hot” Schaudinn’s fluid, chlorophyll extraction in ether, and staining in Harris’ hematoxylin. The entire technique requires less than 90 minutes. 7- A tentative listing of 21 gianera was reported as having been established in the uni algal culture. / Master of Science