Diversity of soft-bottom benthos in a tropical estuary: Gulf of Nicoya,Costa Rica

The community structure of soft-bottom infauna is described for the Gulf of Nicoya, Costa Rica, Central America, with special reference to the relationship between diversity and a tropical estuary. Of the 205 species of invertebrates collected in July, 1980, polychaetes comprised 58.6% by number of species and 68.1% by number of individuals. Density ranged from zero to 8 744 m^-2 with a mean of 1 269 m^-2 per station, and biomass ranged from zero to 10.986 g m^-2 with a mean of 2.010 g m^-2. Numerical analysis indicated considerable faunal homogeneity, characterized by polychaetes. Five major polychaete feeding guilds were recognized. From measures of diversity we concluded that the soft-bottom community of the Gulf of Nicoya was not rich for a tropical estuary. Physical processes (riverine runoff and frontal systems) mainly influenced community structure and function in the lower Gulf whereas biological processes (predation) seemed to prevail in the upper Gulf.Southern California Ocean Studies Consortium Contribution No. 23     

Realizing the potential of GIS in community-based management of protected areas

SUMMARY

This paper explores the roles GIS technology can play in support of land management, focusing in particular on its application in protected environments such as Biosphere Reserves. These ecologically significant areas present complex planning situations since, unlike areas set aside solely for conservation, they must continue to support human populations that depend on natural resources for their economic and social well being. In situations such as marginal tropical locations, land managers often face major economic and political disincentives to the conservation of precious natural resources. The necessity for community participation and local expertise in the planning process becomes increasingly critical as GIS evolves from a basic presentation aid for spatial data to a synthesizing problem-solving tool. Coupled with enhanced community participation is the opportunity for greater education of stakeholders; the potential for GIS to serve as a medium for information gathering and dissemination is discussed. A case study in the Sierra de Manantlán Biosphere Reserve (SMBR), México, is presented.     

Assessing self-organization of plant communities—A thermodynamic approach

Thermodynamics is a powerful tool for the study of system development and has the potential to be applied to studies of ecological complexity. Here, we develop a set of thermodynamic indicators including energy capture and energy dissipation to quantify plant community self-organization. The study ecosystems included a tropical seasonal rainforest, an artificial tropical rainforest, a rubber plantation, and two Chromolaena odorata (L.) R.M. King & H. Robinson communities aged 13 years and 1 year. The communities represent a complexity transect from primary vegetation, to transitional community, economic plantation, and fallows and are typical for Xishuangbanna, southwestern China. The indicators of ecosystem self-organization are sensitive to plant community type and seasonality, and demonstrate that the tropical seasonal rainforest is highly self-organized and plays an important role in local environmental stability via the land surface thermal regulation. The rubber plantation is at a very low level of self-organization as quantified by the thermodynamic indicators, especially during the dry season. The expansion of the area of rubber plantation and shrinkage of tropical seasonal rainforest would likely induce local surface warming and a larger daily temperature range.     

Gill structure in Lucina pectinata (Bivalvia: Lucinidae) with reference to hemoglobin in bivalves with symbiotic sulphur-oxidizing bacteria

Lucina pectinata is a large tropical Lucinidae which is characterized by abundant tissue hemoglobin in its deep-red gills. In the present paper, hemoglobin is described as being located in cytoplasmic dark patches of the bacteriocytes together with a cystine-rich protein. Large microbodies contain a non-hemoglobin heme-compound which is identified with a previously described non-protein-bound hematin; however, it has not been established whether this heme is involved in a sulphur-oxidizing system or represents a catabolic by-product of hemoglobin. Electron-lucent vesicles are associated with the basal microbodies but their function is, so far, unknown. In addition, the bacteriocytes have been observed to have direct contact with sea water, modulated by large intercalary cells which overlap the bacteriocytes on their margin. Such relationships between bacteriocytes and intercalary cells, as well as their cytological features, are different from those observed in lucinid species inhabiting sea-grass beds, but very similar to those observed in Calyptogena magnifica. From the congruence between the shallow-water Lucinidae L. pectinata, inhabiting mangrove swamps, and the deep-sea Vesicomyidae C. magnifica, found at hydrothermal vents, we conclude that such features are likely to be adaptative to high-sulphide environments, notwithstanding the phylogenetic distance.     

广东南部电白小良试验站4种森林群落结构的对比研究

通过对小良试验站不同类型、不同林龄的３种人工林群落（群落Ｂ：桉林;群落Ｃ：松桉混交林;群落Ｄ：阔叶混交林）与当地自然次生热带季雨林（乡土林）相比较,从群落结构的角度探讨人工恢复热带森林的可行性．结果表明：从桉林到松桉混交林到阔叶混交林,３种人工林群落的组成结构和空间结构向着复杂性和稳定性方向发展,并逐渐向地带性自然次生林方向演替;群落的相似性研究也表明,阔叶混交林是３种人工林中与乡土林最为相似．因此,对于极度退化的热带丘陵台地区,在一定工程和生物措施基础上,用先锋绿化树种造林成功后,及时用多层多种的阔叶混交林改造原有先锋林,可以加速人工林向地带性植被类型演替．     

Data on biological productivity of the Western tropical Pacific Ocean

Vertical distribution and production of phytoplankton and planktonic bacteria were studied in the pelagic and neritic regions of the Western tropical Pacific Ocean and in temperate waters of the Japan Sea. The stable, layering structure of the community and its daily fluctuations caused by grazing are described. Data on the integral daily production of communities under 1 m² are presented. The data obtained are discussed with respect to the trophical relations in planktonic communities of the stratified sea basins.     

Slowest of the slow: latitudinal insensitivity of burrowing capacity in the bivalve <Emphasis Type="Italic">Laternula</Emphasis>

Low temperature limits the rate of biochemical reactions and aerobic scopes of cold water ectotherms. To compensate for this limiting effect, animals living in cold environments often possess physiological or morphological adaptations to maintain vital functions. Cross-latitudinal comparison of aerobic capacities is one method to test which factors constrain activity in thermally distinct environments particularly when congeneric studies are carried out on related species with conservative ecology and habitat. Burrowing is a major aerobic activity of bivalve molluscs that is described here for the first time for the tropical mangrove species Laternula truncata and Laternula boschasina and then compared with their Antarctic congener Laternula elliptica. About 80% of L. truncata (16.3–46.1 mm shell length) and 63% of L. boschasina (11.3–27.7 mm shell length) buried within 24 h at 28°C. The burrowing rate index (BRI = [³√wet weight/time to bury]×10⁴) ranged between 1.1 and 20.2 for L. boschasina and 1.1–32.9 for L. truncata. These values are 2–3 orders of magnitude less than other tropical bivalve molluscs and are amongst the lowest recorded for any bivalve. Comparisons with the Antarctic L. elliptica showed little or no differences in BRI (Q ₁₀ of 1.0–1.2 for specimens of the same size). This is contrary to the general pattern over a wide range of bivalves, where BRI increases with a Q ₁₀ of between 2.9 and 6.4 between high latitudes and the equator. L. elliptica has 25–30% longer relative foot length than tropical congeners of the same size, which could be a morphological adaptation compensating for reduced burrowing speeds in a colder environment. Burrowing rates within the genus Laternula could, however, also be maintained by differing habitat, ecological and physiological constraints on burrowing capability.     

Application of temperature gradient gel electrophoresis technique to monitor changes in the structure of the eukaryotic leaf-epiphytic community of <Emphasis Type="Italic">Posidonia oceanica</Emphasis>

Seagrass leaves have been recognized as a suitable substratum in shallow sedimentary environments for the establishment of epiphytic communities. Microscope-based identification of species has been traditionally used to monitor changes in the composition of the eukaryotic leaf-epiphytic community of the seagrass Posidonia oceanica (L.) Delile. Our main goal was to adapt the temperature gradient gel electrophoresis (TGGE) barcoding technique largely used in molecular microbial ecology studies to monitor changes in the composition of P. oceanica epiphytic community. This molecular technique has been successful for handling large amounts of samples in a fast and reproducible manner. To that end, we applied the TGGE technique to study the epiphytic community in two different seasons and compare the results with those provided by the classical microscope approach. The results obtained with both approaches were generally consistent. The complexity of the banding pattern produced by TGGE was mirrored by the taxa richness of the community described using the classical approach. The minimum number of P. oceanica shoots necessary to adequately represent the composition of the eukaryotic leaf-epiphytic community was of the same order of magnitude for both techniques. Partial gene sequences of some selected bands affiliated with sequences of zoo and phytoephytic taxa. Some of them were detected using microscopy. Our results showed that TGGE is an excellent approach for comparative macrobenthic community studies that need parallel treatment of many samples at a time. To the best of our knowledge, this is the first time in which molecular barcoding techniques have been applied to the comparison of eukaryotic epiphytic communities.     

Ecological studies of the coral predator Acanthaster planci in the south pacific

Ecological surveys involving over 500 man-days between 1966 and 1969 indicate that the coral-eating sea star, Acanthaster planci, is a normal component of the coral reef community throughout the tropical Pacific, and that its abundance in the past has probably been underestimated. The sea star is not uncommon in certain environments, particularly back-reef and lagoon slopes. Sheltered, inner reefs are generally preferred over less protected reefs. Recently reported population explosions of A. planci at Guam and on the Great Barrier Reef of Australia appear to be isolated, widely-separated, local infestations of unknown cause. The infestation on the Great Barrier Reef has not spread beyond the area off Cairns and Innisfail. Approximately 40 of the more than 1000 reefs comprising the Great Barrier Reef complex have been infested heavily.     

Specificity of two temperate dinoflagellate–anthozoan associations from the north-western Pacific Ocean

Whilst many studies of symbiotic dinoflagellate diversity have focused on tropical reef environments, only a few have explored the degree and pattern of divergence of these endosymbionts at high latitudes. In this study, the genetic diversity and specificity of symbiotic dinoflagellates associated with two common anthozoan hosts in the north-western Pacific Ocean was studied in four different seasons during a period of 1 year. Partial nucleotide sequences of 28S and complete ITS1 ribosomal DNA regions were used to identify, genetically, the endosymbionts extracted from the scleractinian Alveopora japonica and the actinarian Heteractis sp. A. japonica harbours symbionts belonging to Symbiodinium of clade F, while Heteractis sp. associates with Symbiodinium of clade C. Moreover, no seasonal changes in the endosymbiont community were detected in these two associations during this study. This is the first evidence that these two temperate cnidarian–microalgae symbioses are stable. Furthermore, we tested the apparent specificity of the Heteractis sp.– Symbiodinium sp. clade C association, by performing alga-infection experiments with aposymbiotic hosts, and monitoring the uptake and persistence of homologous and heterologous symbionts. The findings confirm the association patterns detected in the field and show that Heteractis sp. only establishes a successful association with Symbiodinium cells of clade C, at least among the heterologous symbionts occurring in the study area. Our results are consistent with the idea that selective pressures in highly fluctuating temperate environments might have granted symbiosis-specificity an adaptive value.Communicated by T. Ikeda, Hakodate     

Terrestrische ökotoxikologische Testmethoden für die Tropen

Goal, Scope, and Background

Soil organisms play a crucial role in the terrestrial ecosystem. Plant Protection Products (PPPs) are known to affect soil organisms and might have negative impacts on soil functions influenced by these organisms. Little research has been done to day on the impact of PPs on tropical ecosystems. Therefore, in this study it was investigated whether fate and effects of pesticides differ between tropical and temperate regions and whether data generated under temperate conditions can be used for the Environmental Risk Assessment (ERA) in tropical regions.

Methods

In the first part of this study, the effects of two fungicides (Benomyl and Carbendazim) and one insecticide (lambda-Cyhalothrin) on soil invertebrates (i.e. earthworms and arthropods) were evaluated in laboratory tests modified for tropical conditions (temperature, soil, test species). Besides using some native species, the tests were done mainly with two (temperate and tropical) strains of earthworms (Eisenia fetida) and the peregrine isopod speciesPorcellionides pruinosus as standard test species. The chemicals were spiked in two natural and two artificial soils. A tropical artificial soil (TAS), containing a tropical fern product (Xaxim) or coconut coir dust as organic matter, was developed in this study.

Results and Conclusions

The results from the laboratory tests showed that all three test chemicals differed from those gained under temperate conditions. In the case of the fungicides the toxicity was lower but in the case of the insecticide higher under tropical than under temperate conditions. The native tropical earthwormPontoscolex corethrurus reacted more sensitively against Carbendazim in comparison to the standard test speciesEisenia fetida.

Recommendation and Perspective

Details of the environmental risk assessment of the three model chemicals based on the results of the laboratory described here (and including the results of higher tier tests (semi-field and field tests)) will be described in Part 2 of this series     

Marine lakes of karst islands in Ha Long Bay (Vietnam)

Ha Long Bay in North Vietnam is characterized by karst towers and bigger islands totalling more than 3000 isles. Karst processes carved hundreds of caves out of the limestone and contributed to the formation of many enclosed and semi-enclosed saltwater lakes. Here, we report the results of a general survey of several lakes and the first data on the Hang Du I lake, a small basin devoid of any apparent communication with the surrounding sea. Hang Du I is characterized by the presence of Rhizostomeae, genus Mastigias, suggesting strong similarities with the famous lakes described from the archipelago of Palau. Among the benthic organisms sponges are the most important group. Temperature and abundance of the monsoon rains are the main factors influencing remarkable seasonal variations in physical-chemical parameters and the community structure of the lake. A thermal crisis with water temperatures up to 36 °C was recorded in September 2003. In this period, usually abundant medusae and sea anemones totally disappeared. Sponge populations showed fast growth rates in winter and spring and a partial degeneration to face the harsh conditions of the summer season. When isolated from the surrounding marine environment, the saltwater lakes share the condition of oceanic islands, representing spots of habitats surrounded by a completely different environment. The Ha Long Bay marine lakes are not easy to access, being surrounded by tropical forest, but local people usually exploit them for both fishery and oyster harvesting. There is an urgent need to develop measures of protection for these endangered and unique environments, natural laboratories that facilitate the study of evolution of marine organisms, where biodiversity has been until now totally unexplored.     

Exponential Collapse of Benthic Depurative Capacity in A Eutrophic Tropical Marine Ecosystem: A Threshold Response to Organic Nitrogen Loading

Microbial decomposition of particulate organic matter in sediments can substantially modulate eutrophication of nearshore marine environments. Flux budgets for nitrogen compounds and quantification of rates of microbial transformation can provide important information on the process of eutrophication. This survey documents sediment nitrogen budgets for a eutrophic nearshore marine environment at La Parguera on southwest coast of Puerto Rico, including consideration of the organic fraction in addition to microbial transformations.

Sediments of the inshore channel at La Parguera denote the input of heavy organic loads with low redox potentials and high ammonium contents. Benthic fluxes of dissolved organic nitrogen are below those recorded for ammonium. These observations suggest that nearshore tropical sediments subject to heavy nitrogen loads act as a sink for organic nitrogen and that ammonification is a key process in the release of nitrogen from sediments to the water column. Nitrification and denitrification rates are low overall and inversely related to the redox potential. Depuration of excess nitrogen through denitrification is ineffective in these sediments. in contrast to more robust temperate environments, our work demonstrates that tropical marine systems are particularly susceptible to eutrophication given their limited capacity for depuration of excess nitrogen.     

A Contemporary Assessment of Change in Humid Tropical Forests

Abstract: In recent decades the rate and geographic extent of land‐use and land‐cover change has increased throughout the world's humid tropical forests. The pan‐tropical geography of forest change is a challenge to assess, and improved estimates of the human footprint in the tropics are critical to understanding potential changes in biodiversity. We combined recently published and new satellite observations, along with images from Google Earth and a literature review, to estimate the contemporary global extent of deforestation, selective logging, and secondary regrowth in humid tropical forests. Roughly 1.4% of the biome was deforested between 2000 and 2005. As of 2005, about half of the humid tropical forest biome contained 50% or less tree cover. Although not directly comparable to deforestation, geographic estimates of selective logging indicate that at least 20% of the humid tropical forest biome was undergoing some level of timber harvesting between 2000 and 2005. Forest recovery estimates are even less certain, but a compilation of available reports suggests that at least 1.2% of the humid tropical forest biome was in some stage of long‐term secondary regrowth in 2000. Nearly 70% of the regrowth reports indicate forest regeneration in hilly, upland, and mountainous environments considered marginal for large‐scale agriculture and ranching. Our estimates of the human footprint are conservative because they do not resolve very small‐scale deforestation, low‐intensity logging, and unreported secondary regrowth, nor do they incorporate other impacts on tropical forest ecosystems, such as fire and hunting. Our results highlight the enormous geographic extent of forest change throughout the humid tropics and the considerable limitations of the science and technology available for such a synthesis.     

Production of tropical copepods in Kingston Harbour, Jamaica: the importance of small species

The copepod community observed during an 18-month period at the mouth of eutrophic Kingston Harbour, Jamaica, was dominated by small species of Parvocalanus, Temora, Oithona, and Corycaeus. Mean copepod biomass was 22.1 mg AFDW m⁻³ (331 mg m⁻²). Annual production was 1679 kJ m⁻², partitioned as 174 kJ m⁻² naupliar, 936 kJ m⁻² copepodite, 475 kJ m⁻² egg and 93 kJ m⁻² exuvial production. All nauplii, most copepodites and many adults, equivalent to half of the biomass and production, were missed by a standard 200-μm plankton net, emphasizing the importance of nauplii and small species in secondary production estimates. The evidence suggests that growth rates and production are generally not food limited, and we speculate that size-selective predation shapes the structure of the harbour community. Biomass and production are higher than previous estimates for tropical coastal waters, but comparable to other eutrophic tropical embayments and many productive temperate ecosystems. Far from being regions of low productivity, tropical zooplankton communities may have significant production and deserve greater research attention than they currently receive. Received: 19 September 1997 / Accepted: 21 October 1997     

Spatial and temporal variation in growth rates and maturity in the Indo-Pacific squid <Emphasis Type="Italic">Sepioteuthis lessoniana</Emphasis> (Cephalopoda: Loliginidae)

Age, growth and maturity parameters are described for the Indo-Pacific squid Sepioteuthis lessoniana both temporally and spatially (equatorial, tropical and subtropical). Tropical squid that grew through periods of warming water temperatures grew 9% faster than squid that grew through periods of cool water temperatures. The tropical spring-hatched and equatorial squid had similar growth rates (3.24, 3.18 g/day) and these were significantly faster than the tropical summer/autumn hatched squid (2.89 g/day). The oldest squid aged was 224 days, but the majority of individuals were <200 days. Subtropical squid were larger, older and matured later than equatorial and tropical spring-hatched squid. The mean weight of subtropical squid aged between 100 and 150 days was >400 g, 85% greater than tropical and equatorial squid. Geographical differences revealed that subtropical mature winter females and males had mean ages >150 days, respectively 17% and 23% older than their tropical mature winter counterparts. Temporal differences in age at maturity were also evident with tropical winter females and males having a mean age of ~140 days, respectively 41% and 25% older than their summer counterparts. Cooler subtropical and winter tropical squid had the heaviest gonads (>15 g ovaries, >1.5 g testes) compared to summer tropical and equatorial squid. However, relative gonad investment (GSI) values of the cooler squid were significantly lower with cool subtropical and winter tropical females having GSI values <3, which was about half the value of the warmer water females. This study revealed considerable plasticity in the size-at-age of this species. The tropical population had growth parameters that fluctuated between an equatorial strategy (fast growth, small body size, and small gonads) and a subtropical strategy (large body size, slower growth, and large gonads) depending on season.     

Changes in microbial community characteristics and soil organic matter with nitrogen additions in two tropical forests

Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of mechanistic links between microbial responses to N deposition and shifts in soil organic matter (SOM) quality and quantity. We used phospholipid fatty acid (PLFA) analysis and microbial enzyme assays in soils to assess microbial community responses to long-term N additions in two distinct tropical rain forests. We used soil density fractionation and 13C nuclear magnetic resonance (NMR) spectroscopy to measure related changes in SOM pool sizes and chemical quality. Microbial biomass increased in response to N fertilization in both tropical forests and corresponded to declines in pools of low-density SOM. The chemical quality of this soil C pool reflected ecosystem-specific changes in microbial community composition. In the lower-elevation forest, there was an increase in gram-negative bacteria PLFA biomass, and there were significant losses of labile C chemical groups (O-alkyls). In contrast, the upper-elevation tropical forest had an increase in fungal PLFAs with N additions and declines in C groups associated with increased soil C storage (alkyls). The dynamics of microbial enzymatic activities with N addition provided a functional link between changes in microbial community structure and SOM chemistry. Ecosystem-specific changes in microbial community composition are likely to have far-reaching effects on soil carbon storage and cycling. This study indicates that microbial communities in N-rich tropical forests can be sensitive to added N, but we can expect significant variability in how ecosystem structure and function respond to N deposition among tropical forest types.     

小良热带人工窿缘桉林群落结构分析

本文分析了广东小良24龄的人工窿缘桉林的群落结构。结果表明:该群落种类简单,以矮高位芽植物和大型叶植物为主,但建群种窿缘桉不属此列,反映了其生境差的特点;乔木层植物的密度虽小,但叶面积指数大。灌木、草本层植物密度较大,却无窿缘桉幼苗;组成结构分析表明群落的乔木层结构向着简单化或稳定方向发展,而灌木层和草本层向着复杂的方向发展;该群落总的生物量为217.7t/hm~2,其中树干的积累量最大,生产上可以林分改造组建混交林。     

Changes in species composition of demersal fish fauna of Southeast Gulf of Carpentaria,Australia, after 20 years of fishing

The changes in a tropical demersal fish community in the southeast Gulf of Carpentaria, Australia, were examined by comparing the results of a survey undertaken in 1964 before the area was fished, with two surveys in 1985 and 1986 after 20 yr of commercial trawl fishing. The numerical abundance of 52 of the 82 fish taxa had not changed significantly, but that of 18 had decreased while 12 had increased. One taxon (Paramonacanthus spp.) had decreased by more than 500 times and another (Saurida micropectoralis) had increased substantially in abundance. The changes occurred throughout the area surveyed, but the largest changes were offshore. In the pre-trawling community most taxa were caught mainly during the night, while in the post-trawling community most were caught in the same numbers during day and night. In 10 of the 30 taxa that changed in abundance, changes were within a family and could not be explained. For the remaining 20, the changes could be related to their position in the water column: benthic taxa decreased and bentho-pelagic taxa increased. The changes were assessed in relation to fishing effort, and changes in the mud content of the substrate in the study area. Although the changes did not correlate with the fishing effort among three zones in the study area, it is suggested that fishing effort and discarding of the by-catch caused the change in 18 taxa. The magnitude of the decreases of some species might be related to changes in the sediment or possibly other long-term environmental change. There was also a change in the diel behaviour in the fish community that perhaps may be related to the effects of fishing on a tropical multispecies fish community.     

A Regional Perspective on the Diversity and Conservation of Tropical Andean Fishes

Abstract: The tropical Andes harbor an extraordinarily varied concentration of species in a landscape under increasing pressure from human activities. Conservation of the region's native plants and animals has received considerable international attention, but the focus has been on terrestrial biota. The conservation of freshwater fauna, particularly the conservation of fishes, has not been emphasized. Tropical Andean fishes are among the most understudied vertebrates in the world. We estimate that between 400 and 600 fish species inhabit the diverse aquatic environments in the region. Nearly 40% of these species are endemic. Tropical Andean fishes are vulnerable to ongoing environmental changes related to deforestation, water withdrawals, water pollution, species introductions, and hydropower development. Additionally, their distributions and population dynamics may be affected by hydrologic alterations and warmer water temperatures associated with projected climate change. Presently, at least three species are considered extinct, some populations are endangered, and some species are likely to decline or disappear. The long‐term persistence of tropical Andean fishes will depend on greater consideration of freshwater systems in regional conservation initiatives.