Fish assemblages across a complex,tropical freshwater/marine ecotone

Synopsis Riverine fish assemblages in the temperate zone generally show strong longitudinal patterns of faunal turnover and increases in species richness with increasing stream order. We examined the composition and structure of tropical fish assemblages across a complex freshwater/marine ecotone in Tortuguero National Park on the Caribbean coast of Central America. Species turnover was high between four characteristic habitats that largely corresponded with a longitudinal gradient of stream order over distances of less than 30 km. Suites of common fish species characterized each habitat: creeks, rivers, lagoons, and the sea. In addition to the habitat endemics, several species spanned two habitat types, but only three species were collected in more than two habitats. Multivariate gradient analysis of fish assemblages reflected a gradient of habitats that to some extent corresponded to fluvial distances. Due to the unusual configuration of coastal lagoons lying parallel to the coast, the ordination gradient showed little correlation with linear distance to the coast. Environmental variables related to habitat size and salinity showed greatest correspondence with the fish assemblage ordination gradient. Invertebrate-feeding fishes were the predominant trophic group in 15 of 16 fish assemblages, and inland creek sites contained a greater proportion of herbivores and omnivores than other sites. The relative fraction of herbivorous and detritivorous fishes showed a monotonic decline along the longitudinal habitat gradient from inland to coast. Patterns of species composition and richness at Tortuguero Park appeared to agree well with earlier models of factors influencing temperate zone stream fishes. Headwaters have low aquatic primary productivity and contain small colonizing fish species subject to large fluctuations in local densities and intermittent competition. Lagoons contain both large and small species, the latter being restricted largely to shallow edge habitats by predation. Lagoons exhibit more lentic environmental conditions, experience relatively fewer periodic disturbances than headwaters, and their assemblages are inferred to be under relatively greater influence of biotic factors. Fish assemblages of rivers and caños (swampy side channels and braids) appear to be under less abiotic control than headwaters and influenced less by biotic factors than lagoons.     

The early sea life of coho,Oncorhynchus kisutch,and pink salmon,O. gorbuscha,as a period of completion of smoltification

Synopsis Migration, timing and distribution in different salinity zones of Avacha Inlet (Kamchatka) were determine for underyearling pink and yearling coho salmon. Salinity tolerance, RNA/DNA ratio, activity of alkaline phosphatase and level of malonic dialdehyde were investigated in a group of juveniles which migrated quickly to the ocean (smolt) and in another group of fish which stayed in the estuary for a long time (presmolt + smolt). Smolt quality was estimated in downstream migrating pink salmon and compared with groups of presmolt + smolt, smolt, and postsmolt juveniles.     

Relationship of cellular phosphorus in the cyanobacterium Nodularia to phosphorus availability in the Peel-Harvey Estuarine System

A laboratory-determined critical concentration of phosphorus in the cyanobacterium Nodularia spumigena was used to assess the phosphorus sufficiency of field populations in the Peel-Harvey Estuarine System, Western Australia. Nutrient addition bioassays indicated that phosphorus was the limiting nutrient. Since river flow, and thus phosphorus input, to the estuary ceases 1–2 months before the onset of Nodularia blooms, the phosphorus contained in these blooms was derived from sediment release and nutrient recycling. A progressive increase in the mean cellular phosphorus concentration of Nodularia from 1981 to 1983 indicated that sediments were releasing a greater amount of phophorus each year. Although evidence suggests that the biomass of recent Nodularia blooms is now limited by physical factors, the additional phosphorus contained in each bloom will increase the supply of phosphorus to other organisms. Cellular phosphorus concentrations in Nodularia appeared to be correlated with river phosphorus loadings in the Peel Inlet but not in the Harvey Estuary.     

3. NOTES OF THE BIRDS OF THE KRUGER NATIONAL PARK

Mundy. P. J. &; Cook. A. W. 1975. Hatching and rearing of two chicks by the Hooded Vulture. Ostrich 46:45-50

The single-egg clutches of 10 pairs of Hooded Vultures Necrosyrtes monachus were doubled by the addition of one egg to each in the breeding season of 1971/72 at Sokoto, Nigeria. Three pairs hatched both eggs and a further two pairs hatched one egg each. Only one pair raised both chicks to fledging and, apart from a depressed weight gain and tail growth of the younger “sibling”, the chicks grew at approximately the average rate for the species. The average rate was determined by following 27 normal nests in the study area. There was no evidence of aggression between the “siblings”. It was suggested that the success of one adult pair in raising two chicks was partly occasioned by the chicks' ages being only four days apart, and by the unusually rich food supply available from nearby human activities.     

Benthic quality assessment in a naturally- and human-stressed tropical estuary

Cochin estuary, one of the largest tropical estuaries of India, supports high levels of human pressure throughout the year and natural stress during monsoon season. Six stations were monitored between 2002 and 2004 covering the pre-monsoon, monsoon, and post-monsoon seasons. Ecological status of macrobenthos was assessed using the AZTI's Marine Biotic Index (AMBI) and the multivariate-AMBI (M-AMBI). The overall ‘moderate’ disturbance classification (according to AMBI) and ‘moderate-poor’ ecological status (according to M-AMBI) indicate that the macrobenthos in the estuary experiences stress. There was a gradient of increasing quality from the most degraded northern site to the main estuary, downstream. Monsoon caused further reductions in quality of macrobenthos in the main estuary, while the degraded northern station showed improvement in 2003, when the monsoon was strong. The assessment of the Cochin Estuary using AMBI and M-AMBI indicates where this water body stands in comparison to European and other water bodies, which may be useful for developing required protective measures in tropical systems and to design monitoring strategies.     

Substratum preference of the tropical estuarine crabs,Uca tangeri Eydoux (Ocypodidae) and Ocypode cursor Linne (Ocypodidae)

The vertical and horizontal distribution of two burrowing mud crabs, (Ocypodidae) and Ocypode cursor Linne 1758 (Ocypodidae) are described for the Bonny Estuary (7° 00' E: 4° 20′ N), S. Nigeria. Substratum preference is the most prominent factor influencing distribution, but lack of tolerance to low salinities (< 6%_o) is also important, and prevents Ocypode cursor from occurring close to freshwater. The two species have slightly different sediment organic content and grade size requirements. Ocypode cursor was concentrated in well drained sandy sediment above mid-tide-level, whilst Uca tangeri was found in water-logged areas slightly above and below Mid-tide-level. This vertical demarcation is attributed to differential feeding and burrowing adaptations related to different substrata, rather than to differential tolerances to desiccation.     

福建漳江口红树林区秋茄幼苗生长动态

通过福建漳江口红树林自然保护区内8个样方24个小样方人工种植600个秋茄胚轴,在3a时间内对秋茄胚轴建立、幼苗生长以及环境因子进行定期观测。研究结果表明：林缘空地的秋茄生长状况良好,白骨壤林内最不利于秋茄幼苗的生长。潮位、盐度、底质土壤理化因子不是造成该样地各样方间秋茄幼苗生长差异的主要原因。动物取食、光照状况以及种间竞争是限制秋茄生长的主要环境因子。秋茄胚轴在长根前易于随潮水漂走,底质土壤中自骨壤致密的根系抑制了秋茄胚轴的定植,导致白骨壤林内秋茄幼苗漂走的数量最多。昆虫和螃蟹等动物的取食是导致林内已经固着生长的秋茄幼苗大量死亡的最主要原因,而林外被取食的幼苗个体极少。此后秋茄幼苗能否继续成长,主要取决于幼苗所接受到的光照条件。3a后,在荫蔽的树冠下,秋茄幼苗无法存活;而在林外,秋茄幼苗已经长成幼树。在林外滩涂上迅速生长的互花米草,也将影响秋茄幼苗的更新和生长。     

Application of watershed analyses and ecosystem modeling to investigate land–water nutrient coupling processes in the Guadalupe Estuary, Texas

Estuarine nutrient enrichment is thought to be controlled by land use patterns in coastal watersheds. Hence, the objective of this work was to conduct a watershed analysis in two adjacent river basins with different land use characteristics to determine their influence on estuarine ecosystem response in the Guadalupe Estuary, Texas, U.S.A. All data sources for this study were available electronically on the Internet; the data were mined, managed, analyzed and transformed to simulate the estuarine ecosystem response to watershed-derived nutrient loads. Between 1992 and 2001, developed land use/land cover increased the most while forest cover decreased the most in both basins. Two hydrologic units nearest the coast were responsible for the greatest change in land cover. Nutrient concentrations and loads were significantly higher in the San Antonio River Basin than in the Guadalupe River Basin. Both river basins exhibited the highest flows ever recorded in 1992, however the magnitude of difference in loads between the two coastal hydrologic units for a wet and dry year was much greater in the Guadalupe River Basin (GRB) than in the San Antonio River Basin (SARB); this difference supports the concept that the GRB is a nonpoint source dominated system and SARB is a point source dominated system. There was a strong correlation between developed land use and nutrient concentrations in river water; the GRB had less developed land use and lower nutrient concentrations while the SARB had more developed land use and higher nutrient concentrations. Estuarine ecosystem response differed in the timing, duration and magnitude of DIN, phytoplankton and zooplankton when nitrogen loads from the Lower Guadalupe River were used as opposed to the Lower San Antonio. The two basins studied differ in their fundamental characteristics, i.e. precipitation, flow, human population density, etc., resulting in different drivers of nitrogen loading, point sources in the San Antonio River Basin and nonpoint sources in the Guadalupe River Basin, therefore, differing estuarine ecosystem responses.     

生态长江口的概念与构架

2004年作者提出生态长江口概念之后,并没有对其进行过严格的定义。生态长江口是一个符合国家相继提出的实施海洋开发、发展海洋产业和建设生态文明战略的新概念,具有强大的生命力。本文对生态长江口概念进行了定义,并从非原生态型、生态建设型、海洋安全型、生态经济型、生态管理型和生态城市型等6个方面对其内涵进行了诠释,提出了生态长江口的建设目标、指导原则与实施战略构想,探讨了包括建设长江口保护区体系、构建生态长江口安全保障体系和打造生态长江口海岸带经济特区的基本构架。