Conservation and management of the American crocodile

The American crocodile is a rare and endangered species, the range of which has contracted to disjunct locations such as Hispaniola, Jamaica, Cuba, Panama, and southern Florida. In an attempt to determine what factors might be limiting population growth, an extensive collaborative research program was conducted in 1978–82 in southern Florida. Limiting factors explicitly studied included climate, hurricanes, population dispersion, nesting habitat, fertility, predation, nest chamber environment, juvenile survivorship, artificial mortality, disturbance, and environmental contamination. No single natural factor limits the population, although in concert various factors result in low adult recruitment rates. Such natural limitations explain the natural rarity of this tropical species at the temperate limits of its range. Two artificial sources of mortality are death of adults on roads and the flooding of nests by high groundwater tables. These sources of mortality are potentially controllable by the appropriate management agencies. Active management, by such means as protection of individuals, habitat preservation and enhancement, nest site protection, and captive breeding, is also appropriate for assuring the survival of a rare species. The American crocodile has survived in southern Florida in face of extensive human occupancy of parts of its former nesting habitat, demonstrating the resilience of a threatened species. This case history illustrates the efficacy of conducting research aimed at testing specific management hypotheses, the importance of considering biographical constraints limiting population status in peripheral populations, the need for active management of rare species, and the role of multiple reserves in a conservation and management strategy.     

Long-term phytoplankton trends and related water quality trends in the lower Chesapeake Bay,Virginia, USA

Long-term trends (i.e., 1985 through 1999; 14 1/2 yrs) of the phytoplankton community in Chesapeake Bay indicated patterns of increasing phytoplankton abundance and biomass associated with mainly diatoms and chlorophytes, and to a lesser degree dinoflagellates. Decreasing trends in productivity rates above the pycnocline were present over a shorter time period (10 1/2 yrs.), with evidence for increasing nitrogen limitation is indicated. Reduced light availability is inferred due to decreasing trends of Secchi depths and increased suspended solids trends, which were associated with decreasing trends in productivity rates.     

Stormwater toxicity in Chollas Creek and San Diego Bay,California

Stormwater discharges from Chollas Creek, a tributary of San Diego Bay, have been shown to be toxic to aquatic life. The primary objective of this study was to provide the linkage between in-channel measurements and potential impairments in the receiving waters of San Diego Bay. This study addressed this objective within the context of four questions: (1) How much area in San Diego Bay is affected by the discharge plume from Chollas Creek during wet-weather conditions?; (2) How much of the wet-weather discharge plume is toxic to marine aquatic life?; (3) How toxic is this area within the wet-weather discharge plume?; and (4) What are the constituent(s) responsible for the observed toxicity in the wet-weather plume? The stormwater plume emanating from Chollas Creek was dynamic, covering areas up to 2.25 km2. Approximately half of the plume was estimated to be toxic to marine life, based upon the results of purple sea urchin (Strongylocentroutus purpuratus) fertilization tests. The area nearest the creek mouth was the most toxic (NOEC = 3 to 12% plume sample), and the toxicity decreased with distance from the creek mouth. The toxicity of plume samples was directly proportional to the magnitude of plume mixing and dilution until, once outside the plume margin, no toxicity was observed. Trace metals, most likely zinc, were responsible for the observed plume toxicity based upon toxicity identification evaluations (TIEs). Zinc was also the constituent identified from in-channel samples of Chollas Creek stormwater using TIEs on the storms sampled in this study, and in storms sampled during the previous storm season.     

Water quality assessment using integrated modeling and monitoring in Narva Bay, Gulf of Finland

A coupled three-dimensional hydrodynamic–ecological model was used for the assessment of water quality in Narva Bay during one biologically active season. Narva Bay is located in the south-eastern Gulf of Finland. Narva River with a catchment’s area covering part of Russia and Estonia discharges water and nutrients to Narva Bay. The ecological model includes phytoplankton carbon, nitrogen and phosphorus, chlorophyll a, zooplankton, detritus carbon, nitrogen and phosphorus, inorganic nitrogen, inorganic phosphorus and dissolved oxygen as state variables. Both the hydrodynamic and ecosystem models were validated using a limited number of measurements. The hydrodynamic model validation included comparison of time series of currents and temperature and salinity profiles. The ecological model results were compared with the monitoring data of phytoplankton biomass, total nitrogen and phosphorus and dissolved oxygen. The comparison of hydrodynamic parameters, phytoplankton biomass, surface layer total phosphorus and dissolved oxygen and near-bottom layer total nitrogen was reasonable. Time series of spatially mean values and standard deviations of selected parameters were calculated for the whole Narva Bay. Combining model results and monitoring data, the characteristic concentrations of phytoplankton biomass, total nitrogen and phosphorus and near-bottom dissolved oxygen were estimated. Phytoplankton biomass and total phosphorus showed seasonal variations, of 0.6–1.1 and 0.022–0.032 mg/l, respectively, during spring bloom, 0.1–0.3 and 0.015–0.025 mg/l in summer and 0.2–0.6 and 0.017–0.035 mg/l during autumn bloom. Total nitrogen and near-bottom oxygen concentrations were rather steady, being 0.25–0.35 and 2–6 mg/l, respectively. The total nitrogen and phosphorus concentrations show that according to the classification of Estonian coastal waters, Narva Bay water belongs to a good water quality class.     

Metals in tissues of diamondback terrapin from New Jersey

Relatively little is known about contaminants in reptiles, particularly turtles. The distribution of metals in eggs, liverand muscle of diamondback terrapin (Malaclemys terrapin) was examined from Barnegat Bay, New Jersey as part of an aquatic study to understand movement of contaminants in the bay. Lead and cadmium were relatively low in all tissues. There were significant differences among tissues for all metals, except lead. Where there were significant differences, levels werehighest in the liver, except for chromium. Levels of mercurywere 6.6 times higher in the liver than muscle, and manganeselevels were 4 times as high. The levels of metals in muscle ofdiamondback terrapin are below those that might cause effects inconsumers, including humans who eat them in stews. However, thelevel of mercury in liver is sufficiently high to be problematicfor consumers and scavengers that eat liver.     

浙江乐清湾海岸带地区的经济发展

海湾处于陆地和海洋交汇部位,由于开发环境优越,在人类社会发展中占有非常突出的地位.浙江乐清湾海岸带地区在经济迅速发展的同时,也面临着诸如淡水资源缺乏、海洋经济发展层次和城镇化水平偏低等问题.针对这些问题,提出了相应的调控对策和建议.     

杭州湾南岸20 a水质净化功能变化及预测

区域水质净化功能及其影响因素的研究,对深入了解区域水质净化潜力,指导因地制宜的区域总体规划方案与环境保护措施具有重要的现实意义.研究区位于杭州湾南岸,是陆海相互作用的典型区域,承载着重要的经济发展及生态环境功能.基于收集的地形和土地利用类型数据,结合基于站点的气象数据,采用生态系统服务和权衡的综合评估模型（InVEST模型）中的水质净化模型,研究杭州湾南岸氮（N）、磷（P）的负荷量、输出量和净化量的时空演变特征,探索不同发展情境下研究区域水质净化功能的差异.结果表明,时间上,N和P的输出量以及净化量在两年中存在明显差异,相比2000年,2020年研究区域N总负荷量减少276.72 t,输出量减少140.86 t,净化量减少137.86 t;P总负荷量增加93.65 t,输出量增加28.91 t,净化量增加64.74 t;空间上,N、P输出量空间分布趋势大致相同,总体呈现北高南低以及南部部分区域为高值的特征,与土地利用类型密切相关;基于不同情景的模拟分析表明,在自然发展优先情景下,研究区N、P的输出量分别为1 682.36 t和115.50 t,在经济发展优先情景下,区域N、P的输出量分别增加约83.02%和79.93%,在环境保护情景下,区域N、P的输出量分别减少约为79.96%和56.44%.因此环境保护发展优先情景,能有效地减少区域N和P的输出,提高水质净化功能.研究结果为制定区域陆海统筹的规划方案,促进研究区域内经济和生态的协同发展提供了坚实的理论基础.     

地理信息系统支持下的区域环境质量现状评价

针对我国区域环境现状评价工作中的实际问题,在地理信息系统PURSIS的支持下,作者设计了一种离散点插值或趋势面拟合扩展的方法,将以往侧重于监测点逐点评价扩展为在整个空间区域上进行评价,即通过扩展模型获得评价因于浓度空间分布图,在此基础上进行环境因子单项或综合评价。在福建湄洲湾环境质量现状评价中,用这种方法,可以统计出污染物的超标面积及分布区域,并进行年际比较,取得了更为科学、实用的评价结果。     

Assessing a Quick Monitoring Method Using Rocky Intertidal Communities as a Bioindicator: A Multivariate Approach in Algeciras Bay

A multivariate approach was used to test the value of intertidal communities as a bioindicator of environmental conditions at Algeciras Bay, southern Spain. The study area is located in the Strait of Gibraltar and it is subjected to a variety of anthropic impacts. Eight localities (5 inside and 3 outside the bay) were selected, and four transects were undertaken in each locality to characterise the fauna and flora. The spatial distribution of the intertidal species reflected the physico-chemical conditions of Algeciras Bay. The stations located outside the bay, characterised by high hydrodynamism and dissolved oxygen and low sedimentation and turbidity, had a higher diversity and species richness than the inner stations. According to the BIO-ENV procedure and CCA, water turbidity was the factor which best correlated with the intertidal assemblages. SIMPER showed that the molluscs Chtamalus stellatus, Mytilus cf edulis, Littorina neritoides and Balanus perforatus, and the algae Gelidium pusillum, Corallina elongata, Asparagopsis armata, Colpomenia sinuosa and Fucus spiralis were the species that most contributed to the dissimilarity between internal and external sites. The present study, based on the spatial distribution of intertidal taxa, yielded similar results to those previously obtained in the area with costly physico-chemical analysis based on complex matrices of subtidal epifaunal communities. Consequently, the intertidal sampling method proposed in this study is presented here as a quick, effective alternative strategy, and can be useful in environmental monitoring programs, since these communities are easily accessible and amenable to sample, and the sessile nature of the majority of the species makes future, long-term monitoring relatively simple.     

Use of Maryland Biological Stream Survey Data to Determine Effects of Agricultural Riparian Buffers on Measures of Biological Stream Health

This study was undertaken to determine the importance of riparian buffers to stream ecology in agricultural areas. The original Maryland Biological Stream Survey (MBSS) data set was partitioned to represent agricultural sites in Maryland's Coastal Plain and Piedmont regions. ANOVA, multiple linear regression (MLR), and CART regression tree models were developed using riparian and site catchment landscape characteristics. MBSS data were both stratified by physiographic region and analyzed as a combined data set. All models indicated that land management at the site was not the controlling factor for fish IBIs (FIBI) at that site and, hence, using FIBI to evaluate site-scale factors would not be a prudent procedure. Measures of instream habitat and location in the stream network were the dominant explanatory factors for FIBI models. Both CART and MLR models indicated that forest buffers were influential on benthic IBIs (BIBI). Explanatory variables reflected instream conditions, adjacent landscape influence, and chemistry in the Coastal Plains sites, all of which are relatively site specific. However, for Piedmont sites, hydrologic factors were important, in addition to adjacent landscape influence, and chemistry. Both Coastal Plain and Piedmont CART models identified several hydrologic factors, emphasizing the dominant control of hydrology on the physical habitat index (PHI). Riparian buffers were a secondary influence on PHI in the Coastal Plain, but not in the Piedmont. Between 40% and 70% of the variation in FIBI, BIBI, and PHI was explained by the “easily obtainable” variables available from the MBSS data set. While these are empirical results specific to Maryland, the general findings are of use to other locations where the establishment of forest buffers is considered as an aquatic ecosystem restoration measure.