Size-weight relationships and biomass of tropical neritic copepods off Kingston,Jamaica

Nine genera of neritic tropical copepods were collected near Lime Cay, Jamaica, between July 1985 and January 1987. Length-weight regressions were derived for each genus (R ²=0.74 to 0.98), for all calanoids combined (R ²=0.88), and all cyclopoids combined (R ²=0.85). Width-weight regressions were also derived for the same genera but coefficients of determination were generally lower (R ²=0.52 to 0.98) and were much lower forOithona spp. (R ²=0.21). Over a 12 mo period, biomass estimates generated from these length-weight regressions differed by only 3% from direct weight determinations. There were no significant annual variations in prosome lengths for copepodite Stages 1 to 5 inCentropages velificatus, Paracalanus aculeatus orTemora turbinata; prosome lengths in femaleT. turbinata did significantly vary seasonally. No significant seasonal differences in length-weight relationships were observed forC. velificatus. The mean ash content of mixed copepod samples was 6.4%, and the energy density was 25.0 kJ g^–1 AFDW. No significant loss of weight was observed 10 mo after preservation in 10% formalin.     

Abundances,growth rates,and production of tropical neritic copepods off Kingston,Jamaica

Weekly samples were collected near Kingston, Jamaica in 27 m vertical hauls, using 200 and 64µm mesh plankton nets, from July 1985 to January 1987. Thirtytwo copepod species were identified; nauplii and all copepodite stages were enumerated. Total copepod abundance ranged from 2.56 to 87.3 × 10⁴ m^–2. The annual abundance cycle was bimodal with peaks in October–November and May–June corresponding to the rainy seasons. Mean annual copepodite biomass was 0.15 g AFDW m^–2 ranging from 0.03 to 0.41 g AFDW m^–2. Mean generation time (from egg to adult) at 28°C was 19.5 d for the common speciesCentropages velificatus, Paracalanus aculeatus, andTemora turbinata. Isochronal development was demonstrated for copepodites ofP. aculeatus andT. turbinata, but not forC. velificatus. Mean daily specific growth rates (G) were 0.63, 0.63, and 0.48 d^–1 forC. velificatus, P. aculeatus, andT. turbinata, respectively. In general, daily specific growth rates decreased in the later copepodite stages. Thus, it is postulated that growth of later stages and egg production may be food limited. Annual copepodite production was estimated as 419 kJ m^–2 yr^–1, while annual exuvial production and naupliar production were 35 and 50 kJ m^–2 yr^–1, respectively. Egg production was estimated as 44% (184 kJ m^–2 yr^–1) of the total copepodite production. Thus, mean total annual copepod production was 688 kJ m^–2 yr^–1. This estimate is within the range of copepod production estimates in coastal temperate regions.     

A description of a highly diverse soft-bottom community in Kingston Harbour,Jamaica

A highly diverse soft-bottom community in Kingston Harbour, Jamaica is described to provide additional information on the structure of tropical benthic communities. It is shown that the community has a level of diversity unique to stable tropical environments, that dominance by a few species is greatly reduced,and that there are no true parallels to this community in similar environments. The community described seems to fit Sanders' stability-time hypothesis. The density and standing crop of the community are low, and possible explanations for this are discussed. Continuous year-round breeding, short life-spans, and fast turnover rates are suggested as the most important factors regulating biomass in the community described.     

Annual abundance and biomass of aloricate ciliates in tropical neritic waters off Kingston,Jamaica

The daily abundance of aloricate ciliates at Lime Cay, Jamaica, a shallow neritic site, ranged from 29 to 118 × 10⁶ m^–2 (0.97 to 3.93 × 10⁶ m^–3) between November 1985 and November 1986. Biomass was converted to kilojoules (1 kcal=4.1855 kJ) assuming 42% carbon, 20.15 kJ (g dry wt)^–1, and 20% cell shrinkage. Biomass ranged from 0.40 to 3.00 kJ m^–2 (13.3 to 100 J m^–3; 0.28 to 2.08µg C l^–1) with an annual mean of 1.11 kJ m^–2 (36.8 J m^–3; 0.764µg C l^–1). Nanociliates (<20µm equivalent spherical diameter, ESD) dominated abundance, but microciliates (> 20µm ESD) dominated biomass.Strombidium, Strobilidium, Tontonia andLaboea species were conspicuous taxa. Annual production estimates of the aloricate assemblage, based on literature growth rates, ranged from 404 kJ m^–2 yr^–1 (37 J m^–3 d^–1) to 1614 kJ m^–2 yr^–1 (147 J m^–3 d^–1). A compromise estimate of 689 kJ m^–2 yr^–1 (i.e., 63 J m^–3 d^–1) is comparable to other estimates from tropical and subtropical regions. A model of annual energy flow through 11 planktonic compartments suggests the total ciliate assemblage (aloricates and tintinnines) to be as productive as metazoan herbivores and metazoan carnivores.     

Zooplankton growth rates: the influence of size in nauplii of tropical marine copepods

Growth rates and development times were determined for nauplii of the genera: Acartia, Centropages, Corycaeus, Oithona, Paracalanus, Parvocalanus and Temora in nearshore waters of Jamaica from in situ microcosm incubations. At these high local temperatures (∼28 °C), total naupliar development time was short: 3 to 4 d inshore and 4 to 5 d offshore. Mean instantaneous growth rates (g) ranged from as high as 0.90 d⁻¹ for Parvocalanuscrassirostris to as low as 0.41 d⁻¹ for Corycaeus spp. In general, nauplii of cyclopoid copepods appeared to grow more slowly than those of calanoids of the same size. Naupliar growth rates were significantly related to body size (r ²= 0.43 to 0.50), but were unrelated to chlorophyll concentration in any measured size-fraction. This suggests that nauplii are generally not limited by resources, but are growing at their maximum temperature and size-dependent rates. Received: 30 May 1997 / Accepted: 13 May 1998     

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 eutrophication. Phytoplankton biomass (a maximum of 148 mg m^?3 chlorophyll a) was 5 to 10 times greater than in 1971 while zooplankton abundances (maximum of 80,000 animals m^?3) were 4 times greater. in both cases the community composition had altered and there were fewer taxa than previously found.     

Microdistribution of marine copepods in a small inlet

The pattern of microdistribution of 4 species of marine copepods in a small inlet was investigated, based on water samples of 20 l collected successively with a plankton pump. The distribution of each species in a limited area seemed to be related to the hydrographic conditions to some extent; on the other hand, a pattern of non-random and contagions distributions was also clearly indicated. The aggregation of organisms has considerable ecological significance in measurement of the zooplankton production in the sea and the feeding of fish larvae.     

Distribution,structure and importance of the cephalic dorsal hump,a new sensory organ in calanoid copepods

The occurrence, external morphology and internal ultrastructure of a cephalic integumental organ in calanoid copepods were studied, using the specimens from the Pacific, Indian and Atlantic Oceans. This organ is located on the dorsoanterior surface of the cephalosome, and a name, cephalic dorsal hump (CDH) is proposed. Externally, it usually has two pores, anterior and apical, a dorsal plate, and a thin cuticle along the sides. CDH is found only in the male of Calanidae, Megacalanidae, Mecynoceridae and Paracalanidae, and showed some variation between species or species groups both in size and shape. Transmission electron microscopy (TEM) on the specimens from Sagami Bay, Central Japan, revealed that the CDH of Paracalanus parvus and Calanus sinicus consists of two dermal glands and a receptor, which is assumed to be chemosensory. A comparison of the distributions of CDH and prehensile fifth legs of male calanoid copepods suggests that it plays an important role in mate recognition.     

Measuring diversity: the importance of species similarity

Realistic measures of biodiversity should reflect not only the relative abundances of species, but also the differences between them. We present a natural family of diversity measures taking both factors into account. This is not just another addition to the already long list of diversity indices. Instead, a single formula subsumes many of the most popular indices, including Shannon's, Simpson's, species richness, and Rao's quadratic entropy. These popular indices can then be used and understood in a unified way, and the relationships between them are made plain. The new measures are, moreover, effective numbers, so that percentage changes and ratio comparisons of diversity value are meaningful. We advocate the use of diversity profiles, which provide a faithful graphical representation of the shape of a community; they show how the perceived diversity changes as the emphasis shifts from rare to common species. Communities can usefully be compared by comparing their diversity profiles. We show by example that this is a far more subtle method than any relying on a single statistic. Some ecologists view diversity indices with suspicion, questioning whether they are biologically meaningful. By dropping the naive assumption that distinct species have nothing in common, working with effective numbers, and using diversity profiles, we arrive at a system of diversity measurement that should lay much of this suspicion to rest.     

Niche segregation and habitat specialisation of harpacticoid copepods in a tropical seagrass bed

Several harpacticoid copepod species are adapted to an epiphytic lifestyle. Previous studies on tropical seagrass meiofauna mainly focussed on the epiphytic communities and neglected the benthic component. The present study aims to document the benthic harpacticoid copepod communities sampled from different sediment depth horizons adjacent to five seagrass species in the intertidal and subtidal zone of a tropical seagrass bed (Gazi Bay, Kenya). Two benthic copepod communities could be identified mainly based on the tidal position of the samples: a first community was collected near the intertidal seagrasses Halophila ovalis and Halodule wrightii; a second community occurred near the subtidal seagrasses Thalassia hemprichii, Syringodium isoetifolium and Halophila stipulacea. The first community was mainly determined by sediment characteristics (e.g. skewness), while the second community was split off based on organic matter content (% TOM), nutrient and pigment values. A subtle combination of horizontal and vertical niche segregation was reported for the dominant copepod families. Species of the families Thalestridae, Laophontidae and Diosaccidae were structured by tidal position and showed a strong preference for the subtidal zone. The opposite strategy, i.e. a clear preference for the intertidal zone, was found for copepods belonging to the families Paramesochridae and Canuellidae. In addition, Apodopsyllus africanus (Paramesochridae) was well-adapted to stress and was concentrated in the deeper sediment layers near the subtidal seagrasses. On the other hand, Canuellidae, as filter feeders, were concentrated in the upper centimetres of the sediment. The families Ectinosomatidae and Cletodidae did not show any vertical or horizontal segregation. On the species level, however, clear horizontal niche segregation was detected for the family Cletodidae. In addition to the reported ecological results, the study material was used to evaluate different niche definitions. We found tidal position to be the most important factor forcing harpacticoids to specialise. Sediment depth horizon was less powerful in dividing the families into different guilds (from specialists to generalists) based on standardised niche breadth. The present study documents the subtle habitat partitioning of co-existing species in a limited area and its role in sustaining high biodiversity in the community.     

Annual population development and production by small copepods in Disko Bay,western Greenland

The population of small copepod species (approximately <1 mm) were investigated during an annual cycle in Disko Bay, western Greenland. The small species considered were Acartia longiremis, Pseudocalanus spp., Oithona spp., Oncaea spp., Microsetella spp., and Microcalanus spp. Most of the small species were present in the surface waters year round and numerically dominated the community, and in biomass from late summer and throughout winter. Oithona spp. was numerically the main contributor, while Pseudocalanus spp. dominated in terms of biomass. In the uppermost 50 m, maximum abundance, biomass and secondary production were observed in late September after the phytoplankton production practically had terminated and the winter initiated. The free spawning Acartia longiremis showed a strong seasonal fluctuation in biomass and egg production, in contrast to the egg carrying species Pseudocalanus spp. and Oithona spp. These had a long spawning season and maintained a more stable biomass year round. Secondary production was estimated by three different ways: (1) based on the obtained specific egg production rates, (2) a temperature dependent equation, and (3) a multilinear regression taking temperature, body weight and chlorophyll into consideration. The contribution of the small species was insignificant when compared to the large Calanus species during the spring- and post-bloom. However, during late summer and winter, where Calanus had left the upper water strata for hibernation, the small species played a crucial role in the pelagic carbon cycling.     

Comparative life histories of three species of planktonic calanoid copepods in Dabob Bay,Washington

The life history patterns of Calanus marshallae Frost, C. pacificus Brodsky, and Metridia lucens Boeck were determined in Dabob Bay, Washington, USA, during 1973 and October 1981–September 1982. C. marshallae emerged from diapause and moulted to adults in January–February. One major generation was observed, having been produced mainly during early to mid-March. Most surviving individuals spawned in March, arrested development at the C5 stage, and were in diapause by late May. However, some individuals developed to adults by late April and produced a very minor second generation. C. pacificus emerged from diapause and moulted to adults in February–March. The first generation produced during the spring lagged slightly behind the C. marshallae generation. C. pacificus produced two additional generations, one in late spring and one in the fall. The production of the three generations coincided with or closely followed phytoplankton blooms. Some C. pacificus arrested development at the C5 stage and entered diapause during the summer, but the majority of the population did not do so until fall. M. lucens did not appear to enter a diapause state. The fall and winter population was chiefly adult females which mostly remained at depth and were reproductively immature. Nevertheless, naupliar M. lucens were found on all sampling dates, indicating that reproduction never ceased as it did for the two Calanus species. M. lucens produced generations in late winter/early spring, late spring, and late summer/early fall. Interspecific comparisons between the life histories observed in Dabob Bay and intraspecific comparisons between the life histories in Dabob Bay and other locations are made. The advantages or disadvantages conferred to the copepods by their differing life histories are also discussed.     

Zooplankton growth rates: the influence of female size and resources on egg production of tropical marine copepods

Egg production was measured in 17 species of copepods from the genera Acartia, Calanopia, Centropages, Clausocalanus, Corycaeus, Eucheata, Euterpina, Oithona, Oncaea, Paracalanus, Parvocalanus, Temora and Undinula in Jamaican waters. At the high local temperatures (∼28 °C), mean egg production ranged from 3.2 to 88 eggs female^–1 d^–1, and instantaneous female growth (g, as egg production) ranged from 0.04 to 0.87 d^–1. Female growth was positively related to ambient chlorophyll concentration (r ² = 0.44) and negatively to female body size (r ² = 0.29). Together these two variables explained 60% of the variation in growth. When quadratic terms for chlorophyll and a term for interaction of body size and chlorophyll were introduced, 82% of the variance in growth rate was explained. Egg production rates represent an extension of the resource and size-dependent relationship established for copepodites. In smaller species (<3.5 μg), egg production was comparable to prior copepodite somatic growth; in larger species (>3.5 μg), egg production is compromised at lower resource concentrations than copepodite somatic growth. Thus, it appears that egg production in tropical copepods may be frequently limited by resources in a size-dependent manner. Under conditions where growth is resource limited, we caution against the application of egg production rates for the calculation of total copepod production. Received: 30 May 1997 / Accepted: 13 May 1998     

Mosaic horizontal distributions of three species of copepods in the subarctic Pacific during spring

 Continuous abundance estimates (510 m resolution) of the copepods Neocalanus cristatus, N. flemingeri and Metridia pacifica were obtained with an electronic particle counter along cruise tracks in the subarctic western North Pacific in spring. For all three species, the number of patches decreased exponentially with increasing patch size. Most patches (63 to 83%) were dominated by one species, and patches of the same species more closely spaced than patches of different species. The patches of M. pacifica tended to coexist with those of N. cristatus. In contrast, patches of N. flemingeri rarely co-occurred with those of other copepods. These patterns were more clearly observed in fine-scale observations with sampling intervals of <31 m. Coherence analysis of copepod species pairs showed no characteristic scale at 2 to 50 km wave lengths. At shorter wave lengths (<2 km), frequent positive correlations were observed between N. cristatus and M. pacifica. Thus, the distribution of copepods appears to be a mosaic assemblage of patches of each copepod species. These results suggest that copepods have a mechanism to form species-specific aggregations, and the aggregation and segregation processes are maintained at a scale of <2 km. Received: 24 February 1999 / Accepted: 25 April 2000     

Biology of small juveniles of the tropical holothurian Actinopyga echinites: growth,mortality, and habitat preferences

Several morphological, physiological and ecological experiments on the general biology of small juveniles (drained body weight=0.09 to 17.34 g) of Actinopyga echinites (Jäger 1833) (Echinodermata, Holothuroidea) were conducted between August 1991 and July 1992 at Bise reef flat, Okinawa, southern Japan. Supplementary experiments were carried out at the laboratory. The experiments were designed with a view to potential stock enhancement projects of A. echinites and other commercially exploited tropical sea cucumbers of the coral reef zone. During the enclosure experiments, the average percentage of drained body weight to fresh body weight of the juveniles was 48.3%. The specimens displayed a growth rate of 1500% during the 11-mo period. Their drained body weight increased from 0.87 to 12.82 g. The juveniles' internal and skeletal morphology differed considerably from the morphology of adult A. echinites. Two new types of skeletal spicules were discovered. Individual growth of all spicule types monitored differed notably, and shrinkage was observed for the two newly discovered types. Relative frequency of the spicule types within the skeletons changed with increasing body weights of the individuals. The juveniles of A. echinites displayed a strong habitat preference for plate-like substrate types such as eroded limestone or dead coral plates. Skeletons of Acropora spp. were accepted at a much lower rate. Weight-frequency distributions of the specimens on varying substrate types and between various times of the day showed significant differences. Cryptic behaviour of the juveniles was observed at all times of the day. Natural mortality of the holothurians, excluding predation and minor dislodgement effects, was low at 0.6% mo^–1. When predation effects were introduced to the experiments, mortality reached a rate of 0.3% mo^–1. The average percentage of predation effects within the natural mortality total was 76.8%. Juvenile A. echinites exhibited a maximum short-distance migration speed of 9 cm h^–1. This was two orders of magnitude slower than the speed observed in adults (900 cm h^–1) when differences in total body length were taken into consideration. The holothurians had two activity peaks during the 4-h periods monitored, around sunrise and sunset, respectively.     

Seasonal variation in lipid class and fatty acid composition of two small copepods in Balsfjorden,northern Norway

Zooplankton were collected at Svartnes, northern Norway between 1985 and 1986. The lipid class and fatty acid composition of a subarctic population ofPseudocalanus acuspes (Giesbrecht, 1881) andAcartia longiremis Lilljeborg are described for four seasons of the year. The results are discussed in relation to the seasonal variation in abundance and dry weight of the predominant developmental stages. The lipid composition of these small copepod species resembles that of omnivorous or carnivorous species.P. acuspes andA. longiremis overwinter in a state of arrested development, but seem to feed actively throughout the year. This behaviour resembles that of the omnivoreMetridia longa (Lubbock), but is in contrast to that of the herbivoreCalanus finmarchicus (Gunnerus) from the same area, which spends the winter in diapause.     

Influences of abundance,behavior, species composition,and ontogenetic stage on active emergence of meiobenthic copepods in subtropical habitats

The emergence of meiobenthic copepods in subtidal sand and seagrass sites in Tampa Bay, Florida (USA), was investigated on nine dates from March 1983 to August 1984. Numbers of emerging copepods were dependent on habitat, date and diel sampling period. Greater numbers typically emerged in seagrass sites, and differences between habitats may be related to lower copepod abundances in sand sites. Both copepod abundance and behavior significantly affected numbers emerging among dates. An increase in emergent behavior alone resulted in consistently greater numbers emerging during postsunset periods. Over 30 species in 15 families were found to emerge. Total numbers of emerging copepods were affected by the sporadic presence and seasonal behavior of certain species. Numbers of the predominant speciesParadactylopodia brevicornis, Tisbe furcata, Parategastes sp.,Mesochra pygmea, Laophontid sp., andHarpacticus sp. emerging depended on differences in both species abundance and behavior. The emergent behavior ofParategastes sp.,Harpacticus sp., andT. furcata also was influenced by total copepod densities in the sediment. Juvenile copepods constituted only a small proportion of the total numbers emerging. The consistent postsunset entry of between 10³ to 10⁵ copepods m^?2 into the water column in subtidal sand and seagrass habitats will contribute to the increased probability of copepod dispersal and reassortment of the benthic community, while providing a pathway for benthic-pelagic exchange.     

Directional changes in the species composition of a tropical forest

Long-term studies have revealed that the structure and dynamics of many tropical forests are changing, but the causes and consequences of these changes remain debated. To learn more about the forces driving changes within tropical forests, we investigated shifts in tree species composition over the past 25 years within the 50-ha Forest Dynamics Plot on Barro Colorado Island (BCI), Panama, and examined how observed patterns relate to predictions of (1) random population fluctuations, (2) carbon fertilization, (3) succession from past disturbance, (4) recovery from an extreme El Ni?o drought at the start of the study period, and (5) long-term climate change. We found that there have been consistent and directional changes in the tree species composition. These shifts have led to increased relative representations of drought-tolerant species as determined by the species' occurrence both across a gradient of soil moisture within BCI and across a wider precipitation gradient from a dry forest near the Pacific coast of Panama to a wet forest near its Caribbean coast. These nonrandom changes cannot be explained by stochastic fluctuations or carbon fertilization. They may be the legacy of the El Ni?o drought, or alternatively, potentially reflect increased aridity due to long-term climate change. By investigating compositional changes, we increased not only our understanding of the ecology of tropical forests and their responses to large-scale disturbances, but also our ability to predict how future global change will impact some of the critical services provided by these important ecosystems.     

Temporal patterns in diversity and species composition of deep-sea benthic copepods in bathyal Sagami Bay,central Japan

Little is known about temporal changes in the diversity and species composition of deep-sea metazoan meiofauna and their relationships with changes in the food supply. Those changes were studied for benthic copepod assemblages based on 2-year time-series data at a bathyal site in Sagami Bay (1430 m depth), central Japan, where annual fluctuation in the abundance of benthic foraminiferans was previously observed. Species diversity of benthic copepods at the site was as high as, or slightly higher than, that observed at other deep-sea sites, but did not fluctuate temporally through the study period. Multivariate analyses did not reveal any clear seasonal or directional change occurring over the longer term in their species composition, although there was some consistent pattern. These results indicate a lack of, or only weak, seasonality in the diversity and species structure of the deep-sea benthic copepod assemblages, even though the fresh organic food supply fluctuates seasonally. They also suggest that there are differences between copepods and foraminiferans in the response to changes in environmental factors, and that spatial differences in the composition of copepod communities are greater than temporal ones at this deep-sea site.Communicated by T. Ikeda, Hakodate