You have entered the website of the Water and Environmental Research Institute of the Western Pacific (WERI) at the University of Guam. We are currently six faculty and five staff and our mission is to seek solutions through research, teaching and outreach programs, to issues and problems associated with the location, production, distribution and management of freshwater resources in Guam, the CNMI and the FSM.
Glass slides were immersed quarterly in five bodies of fresh water (polluted and unpolluted) for 10 to 14 days to collect periphytic diatoms. Concurrent with the periphyton collection period, water samples were collected on three separate days and analyzed for 22 water quality parameters. Natural surfaces (plants, rocks and sediments) were also collected and the inhabitant diatom assemblages analyzed to compare with the glass slide collections. Diatom collections were analyzed by randomly selecting an area on an exposure slide (or prepared cover slip) and counting at least 750 diatom frustules, identifying individuals to species. This data was used to calculate species diversity indices (Shannon-Wiener function and Simpson's index), a similarity index, and to determine if diatom assemblages occur according to a water quality or habitat type.
Results revealed that bodies of water derived from or containing urban runoff can be expected to have diatom assemblages dominated by Nitzschia palea and have low species diversity. This response is particularly evident where nutrient (NO3-N and PO4-P) enrichment occurs. In extreme cases the diatoms (primarily Navicula palea) are replaced by blue-green algae (a mixture of Oscillatoria, Spirulina and Anabaena spp.).
In ponded habitats where the concentrations of mineralized nutrients were excessively low (< 0.020 mg/L), Gomphonema parvulum dominated the diatom assemblage. Diatom coverage of the slides at this site was the lowest observed. In polluted small rivers (average flow < 1.0 mgd), diatom assemblages were more diverse and were dominated by Gomphonema clevei. The high degree of sample similarity between river stations over time indicates that distinct diatom assemblages exist according to water quality and habitat types.
Comparisons of diatom assemblages occurring on natural substrata with those collected on glass slides showed reduced species numbers (over 33%) and species diversity occurring on the glass slide samples. However, this may have resulted in part or in total from the fact that there was no time limitation for diatom colonization of the natural surfaces. However, the glass slides did collect diatoms from all the habitats (epiphytic, epipelic, and epilithic) since the dominant species in the natural substrata collections were also found on the slides.
