Effects of water from Nakhodka Bay (Peter the Great Bay, Sea of Japan) on the early development of the Sea UrchinStrongylocentrotus intermedius

Our studies show that seawater from different sites in Nakhodka Bay has a deleterious effect on the development of the sea urchinStrongylocentrotus intermedius. As development proceeded to the pluteus I stage, the percentage of abnormal larvae maintained in water from Nakhodka, Novitskogo, and Vrangelya Bights increased markedly (66.7±2.2, 67.1±2.6, and 54.6±1.8%, respectively). These larvae developed more slowly, were smaller, and differed from those in the control in the intensity of color of their echinochrome granules. In water from Nakhodka and Novitskogo bights, larval survival rates were lower than in the control. This suggests that the water of Nakhodka Bay is heavily polluted, especially in its harbor areas.     

沉积物再悬浮对浮游藻类影响的模拟实验研究

作为浅水湖泊的重要特性之一,由风浪等动力作用引起的沉积物再悬浮对浮游藻类的初级生产力、群落结构具有重要意义。本研究通过生长季节(5-6月)在太湖梅梁湾湖岸的中宇宙模拟实验,比较在同样的外源负荷下浮游藻类对不同的沉积物再悬浮程度的影响特征,以及其主要的影响因子。实验在约250L的大桶中进行,通过位于沉积物-水界面的水泵的动力作用,模拟了三个不同程度沉积物再悬浮:无再悬浮即对照、弱悬浮和强悬浮程度。实验结果显示:(1)对照、弱悬浮和强悬浮之间悬浮物浓度呈显著性梯度变化,平均值分别为5、30、40 mg L-1,水下20cm光密度分别为表面光密度的80%、35%和25%。TN和TP在悬浮处理组显著高于对照组,但是弱悬浮和强悬浮之间差异不显著。生物可利用的各种溶解性营养盐形式对再悬浮的响应特征不明显。(2)浮游藻类生物量和群落结构对再悬浮的响应显著。对照组的Chla在整个实验阶段都很低,强悬浮组和弱悬浮组的平均Chla分别5倍和2倍于对照组。实验初始浮游藻类群落种类多样性低,优势种群主要为隐藻(隐藻属Cryptomonas spp.和蓝隐藻Chroomonas acuta)。再悬浮处理显著促进了隐藻的生长,但弱悬浮和强悬浮之间差异不显著。对照组优势种群演替为微小型种类蓝隐藻和绿藻门的纤维藻属(Ankistrodesmus sp.)。(3)以相对丰度为统计数据,浮游动物群落结构对再悬浮的响应显著,弱悬浮和强悬浮之间差异不显著。对照组的枝角类大型种类溞属(Daphnia spp.)丰度显著高于再悬浮处理组,枝角类小型种类象鼻溞属(Bosmina spp.)和网纹溞属(Ceriodaphnia spp.)、轮虫丰度则呈相反趋势。可见,再悬浮促进了沉积物营养盐的释放和水下光照的衰减,还影响了浮游动物的群落结构,使其向摄食藻类能力较差的种类演替,从而在上行(bottom-up)和下行(top-down)两个方面影响了浮游藻类的现存量和群落结构。     

Carbonic anhydrase inhibition blocks skeletogenesis and echinochrome production in Paracentrotus lividus and Heliocidaris tuberculata embryos and larvae

Carbonic anhydrases (CAs) are a family of widely distributed metalloenzymes, involved in diverse physiological processes. These enzymes catalyse the reversible conversion of carbon dioxide to protons and bicarbonate. At least 19 genes encoding for CAs have been identified in the sea urchin genome, with one of these localized to the skeletogenic mesoderm (primary mesenchyme cells, PMCs). We investigated the effects of a specific inhibitor of CA, acetazolamide (AZ), on development of two sea urchin species with contrasting investment in skeleton production, Paracentrotus lividus and Heliocidaris tuberculata, to determine the role of CA on PMC differentiation, skeletogenesis and on non‐skeletogenic mesodermal (NSM) cells. Embryos were cultured in the presence of AZ from the blastula stage prior to skeleton formation and development to the larval stage was monitored. At the dose of 8 mmol/L AZ, 98% and 90% of P. lividus and H. tuberculata embryos lacked skeleton, respectively. Nevertheless, an almost normal PMC differentiation was indicated by the expression of msp130, a PMC‐specific marker. Strikingly, the AZ‐treated embryos also lacked the echinochrome pigment produced by the pigment cells, a subpopulation of NSM cells with immune activities within the larva. Conversely, all ectoderm and endoderm derivatives and other subpopulations of mesoderm developed normally. The inhibitory effects of AZ were completely reversed after removal of the inhibitor from the medium. Our data, together with new information concerning the involvement of CA on skeleton formation, provide evidence for the first time of a possible role of the CAs in larval immune pigment cells.     

Similar temperature responses suggest future climate warming will not alter partitioning between denitrification and anammox in temperate marine sediments

Removal of biologically available nitrogen (N) by the microbially mediated processes denitrification and anaerobic ammonium oxidation (anammox) affects ecosystem N availability. Although few studies have examined temperature responses of denitrification and anammox, previous work suggests that denitrification could become more important than anammox in response to climate warming. To test this hypothesis, we determined whether temperature responses of denitrification and anammox differed in shelf and estuarine sediments from coastal Rhode Island over a seasonal cycle. The influence of temperature and organic C availability was further assessed in a 12‐week laboratory microcosm experiment. Temperature responses, as characterized by thermal optima (T_opt) and apparent activation energy (E_a), were determined by measuring potential rates of denitrification and anammox at 31 discrete temperatures ranging from 3 to 59 °C. With a few exceptions, T_opt and E_a of denitrification and anammox did not differ in Rhode Island sediments over the seasonal cycle. In microcosm sediments, E_a was somewhat lower for anammox compared to denitrification across all treatments. However, T_opt did not differ between processes, and neither E_a nor T_opt changed with warming or carbon addition. Thus, the two processes behaved similarly in terms of temperature responses, and these responses were not influenced by warming. This led us to reject the hypothesis that anammox is more cold‐adapted than denitrification in our study system. Overall, our study suggests that temperature responses of both processes can be accurately modeled for temperate regions in the future using a single set of parameters, which are likely not to change over the next century as a result of predicted climate warming. We further conclude that climate warming will not directly alter the partitioning of N flow through anammox and denitrification.     

Upslope development of a tidal marsh as a function of upland land use

To thrive in a time of rapid sea‐level rise, tidal marshes will need to migrate upslope into adjacent uplands. Yet little is known about the mechanics of this process, especially in urbanized estuaries, where the adjacent upland is likely to be a mowed lawn rather than a wooded natural area. We studied marsh migration in a Long Island Sound salt marsh using detailed hydrologic, edaphic, and biotic sampling along marsh‐to‐upland transects in both wooded and lawn environments. We found that the overall pace of marsh development was largely unaffected by whether the upland being invaded was lawn or wooded, but the marsh‐edge plant communities that developed in these two environments were quite different, and some indicators (soil salinity, foraminifera) appeared to migrate more easily into lawns. In addition, we found that different aspects of marsh structure and function migrated at different rates: Wetland vegetation appeared to be a leading indicator of marsh migration, while soil characteristics such as redox potential and surface salinity developed later in the process. We defined a ‘hydrologic migration zone’, consisting of elevations that experience tidal inundation with frequencies ranging from 20% to 0.5% of high tides. This hydrologically defined zone – which extended to an elevation higher than the highest astronomical tide datum – captured the biotic and edaphic marsh‐upland ecotone. Tidal inundation at the upper border of this migration zone is highly variable over time and may be rising more rapidly than mean sea level. Our results indicate that land management practices at the upland periphery of tidal marshes can facilitate or impede ecosystem migration in response to rising sea level. These findings are applicable to large areas of tidal marsh along the U.S. Atlantic coast and in other urbanized coastal settings.     

A meta‐analysis of soil salinization effects on nitrogen pools,cycles and fluxes in coastal ecosystems

Salinity intrusion caused by land subsidence resulting from increasing groundwater abstraction, decreasing river sediment loads and increasing sea level because of climate change has caused widespread soil salinization in coastal ecosystems. Soil salinization may greatly alter nitrogen (N) cycling in coastal ecosystems. However, a comprehensive understanding of the effects of soil salinization on ecosystem N pools, cycling processes and fluxes is not available for coastal ecosystems. Therefore, we compiled data from 551 observations from 21 peer‐reviewed papers and conducted a meta‐analysis of experimental soil salinization effects on 19 variables related to N pools, cycling processes and fluxes in coastal ecosystems. Our results showed that the effects of soil salinization varied across different ecosystem types and salinity levels. Soil salinization increased plant N content (18%), soil NH₄⁺ (12%) and soil total N (210%), although it decreased soil NO₃^? (2%) and soil microbial biomass N (74%). Increasing soil salinity stimulated soil N₂O fluxes as well as hydrological NH₄⁺ and NO₂^? fluxes more than threefold, although it decreased the hydrological dissolved organic nitrogen (DON) flux (59%). Soil salinization also increased the net N mineralization by 70%, although salinization effects were not observed on the net nitrification, denitrification and dissimilatory nitrate reduction to ammonium in this meta‐analysis. Overall, this meta‐analysis improves our understanding of the responses of ecosystem N cycling to soil salinization, identifies knowledge gaps and highlights the urgent need for studies on the effects of soil salinization on coastal agro‐ecosystem and microbial N immobilization. Additional increases in knowledge are critical for designing sustainable adaptation measures to the predicted intrusion of salinity intrusion so that the productivity of coastal agro‐ecosystems can be maintained or improved and the N losses and pollution of the natural environment can be minimized.     

Enhancing the performance of hazard indexes in assessing hot spots of harbour areas by considering hydrodynamic parameters

The hazard assessment strategies for harbour areas usually rely on tools able to predict environmental threats posed by contaminated sediments, mostly based on biological and chemical parameters and distinctly less on hydrological factors. Although ports are considered semi-enclosed and low-energy systems with scarce capacity to disperse contaminants to the open sea, the hydrological pattern established within the port basin cannot be neglected, especially when the localisation of hot spots is required for clean-up and remediation actions. In the present study we considered both approaches (biological/chemical and hydrological) for assessing hot spots of harbour areas. In particular, the relationship between the sediment hazard assessment c_NWAC (cumulative Normalized and Weighted Average Concentration) index (which is based on chemical and biological data) and a properly selected hydrodynamic parameter (the bottom shear stress) of the port area was investigated. This study demonstrates that marine currents influence significantly the fine-grained fraction distribution of the surficial sediments, and thus, the spatial and temporal variability of contaminant concentration. The evaluation of hydrodynamic parameters enhances the performance of hazard tools in the localization of areas of most concern and thus a detailed knowledge of the hydrodynamic features of the port seabed is advisable before defining a proper characterisation strategy for the harbour area.