Mona K. Webber

Annual biomass and production of the oceanic copepod community off Discovery Bay, Jamaica

Monthly samples were collected in oceanic waters off Discovery Bay, Jamaica, in 60- and 200-m vertical hauls, using 200- and 64-μm mesh plankton nets, from June 1989 to July 1991. Length-weight regressions were derived for twelve genera of copepods (R2=0.79 to 0.97). For eight occasions spanning the study period, biomass estimates generated from these length-weight regressions differed by only 3% from direct weight determinations. The mean ash content of copepods was 7.1%, and the energy density was 20.8 kJ g-1 ash-free dry weight (AFDW). Mean annual biomass of the total copepod community in the upper 60 m was 1.83 mg AFDW m-3 (range 1.14 to 2.89 mg AFDW m-3), and for the 200-m water column was 0.96 mg AFDW m-3 (range 0.12 to 1.99 mg AFDW m-3). Estimates of generation times for five common taxa ranged from 16.1 to 33.4 d. None of the taxa investigated displayed isochronal development; in general, stage duration increased in later copepodite stages. Weight increments showed a significant decrease in later copepodite stages, but with strong reversal of the trend from stage 5 to adult female in most species. Daily specific growth rates also declined in later copepodite stages, and ranged from 1.49 d-1 in stage 1–2 Paracalanus/Clausocalanus spp. to 0.04 in stage 5-female of Oithona plumifera. Progressive food limitation of somatic copepodite growth and egg production is postulated. Naupliar production was 50.4 to 59.5% of copepodite production, and egg production was 35.1 to 27.7% of copepodite production in the 60-and 200-m water columns, respectively. Total annual copepod production, including copepodites, nauplii, eggs and exuviae, was 160 kJ m-2 yr-1 for the upper 60 m and 304 kJ m-2 yr-1 for the upper 200 m. Secondary production of the copepod community in oceanic waters off Discovery Bay approaches 50% of the corresponding value in tropical neritic waters.

Annual structure of the copepod community and its associated pelagic environment off Discovery Bay, Jamaica

Monthly samples were collected in oceanic waters off Discovery Bay, Jamaica, in 60- and 200-m vertical hauls, using 200- and 64-μm mesh plankton nets, from June 1989 to July 1991. Sixty-nine species of copepods were identified: nauplii, copepodites and adults were separately enumerated. Total copepod abundances (all stages) ranged from 695 to 4120 m-3 in the upper 60 m, and from 483 to 3319 m-3 in the 200-m water column, without any clear seasonal pattern. With the exception of temperature, no seasonal variations in physico-chemical (chlorophyll a, S‰, particulate organic carbon, particulate protein) or biological variables were evident. Nauplii, adults and copepodites of selected taxa, and two chaetognath species, showed no significant variations in body length. Significant variantions in reproductive index were detected for several species, but without seasonal trends; many species appear to be continuous or intermittent breeders. There was no evidence of seasonal pattern in overall community composition or diversity, or evidence of changes due to water mass advection. The copepod community can be divided into a recurrent group of 13 (at 60 m) to 17 (at 200 m) “perennial” species, present year-round, and associated “ephemeral” groups of 1 to 3 species, present randomly for 1 to 4 consecutive months. The most plausible explanation of these patterns is that broad areas of the Caribbean Sea are dominated by the community of perennial species, while the ephemeral species represent the superimposed influence of local mesoscale gyres.

The Water Quality of Kingston Harbour: Evaluating the Use of the Planktonic Community and Traditional Water Quality Indices

Abstract Kingston Harbour has been experiencing increased levels of organic pollution since initial ecological assessments in 1971. to develop a new baseline of eutrophication in the Harbour 20 years later, and determine the most appropriate indices to be used in the continued monitoring the area, the water quality of Kingston Harbour was reassessed between December 1992 and 1993, by contemporaneous sampling of traditional water column parameters and planktonic communities at 28 stations within the Harbour. Indices used for water quality assessment were temperature, salinity, light penetration, dissolved oxygen, BOD and nutrients (nitrates-N, phosphate-P and ammonia-N). Results indicated that the planktonic community provided the most reliable index of increased eutrophication and changes in water quality. While physical variables indicated little change in Harbour waters and chemical variables indicated significant but erratic changes, the planktonic community displayed the classic characteristics of eut...

Effects of flood waters on the planktonic community of the Hellshire coast, Southeast Jamaica

Between 24 May and 4 June 1986, the island of Jamaica experienced up to 635 mm of rainfall producing islandwide flooding. Planktonic communities along the south coast were studied before and after the flooding. Flood waters from Kingston Harbour flowed southwest along the Hellshire coast as far as Wreck Reef, but were confined within 4 km of the shore. Water in the bays along the lower Hellshire coast remained clear and unaffected by Harbour water, although planktonic communities there showed marked changes. The Port Royal Cays area and much of the shelf was unaffected (...)

The Use of Ecopath Software to Model Trophic Interactions within the Zooplankton Community of Discovery Bay, Jamaica

Ecopath with Ecosim 5.1 software was used to formulate a reasonable model of the trophic interactions within the zooplankton community in Discovery Bay, Jamaica W.I. The zooplankton were separated into functional groups and, for each functional group, the software required the input of at least four basic parameters as well as the diet composition for each consumer group. These parameters included: biomass; production/biomass ratio; consumption/biomass ratio and ecotrophic efficiency. The model generated indicated that, with respect to the zooplankton community, Discovery Bay is a developing ecosystem which would not be particularly resistant to perturbations. It would therefore be unable to easily recover from significant stresses (eutrophication; increased fishing efforts etc.) imposed on the ecosystem, indicating the need for both short-term and long-term management strategies based on the level of use (or planned usage) of the bay.