Tidal impact on planktonic primary and bacterial production in the German Wadden Sea

 Tidal variation of biological parameters was studied at three anchor stations in selected inlet channels of the northern German Wadden Sea in May and July 1994. Concentrations of bacteria, chlorophyll a and suspended matter as well as primary and bacterial production were assessed over a period of 25 h in the surface and in the bottom water. Diurnal variation in primary production was found both under in situ light conditions and under constant illumination. Tidal turbulence caused the introduction of detritus, bacteria and pigments from the sediment into the water column. The impact of sediment resuspension was most evident in the bottom water, leading to tidally oscillating bacterial production rates which were high during high stream velocity and low during the slack times. Estimations of the areal daily phytoplankton production and corresponding bacterial carbon demands were unbalanced. Primary production accounted for only 25–45% of the total bacterial carbon requirement. This discrepancy is due to the shallow euphotic depth in the Wadden Sea, allowing net primary production only in the upper 2–3 m of the water column, while the relatively high levels of bacterial activity do not show a vertical decline. Assuming that the specific biological activities in the water columns over the tidal flats are similar to those found in the inlet channels, it was found that production processes dominate in shallow areas whereas decomposition processes dominate in the deep channels. Moreover, the predominance of heterotrophic processes in the inlet channels means that additional organic carbon sources must contribute to the heterotrophic metabolism in the deep parts of the Wadden Sea, and that the horizontal flux of material is important in this turbid mesotidal ecosystem. Received: 18 April 1998 / Accepted: 12 November 1998     

Tidal Flow in Riverine-Type Mangroves

The behavior of tidal flow in the riverine-forest type is investigated in the Aira-River mangrove area in Iriomote Island, Japan. In the mangrove swamp near the bank of the creek, a velocity component parallel to a tidal creek reduces greatly in the direction perpendicular to the creek. Based on this finding, it is theoretically suggested that the eddy viscosity in the mangrove swamp, which is caused by the interaction between mangrove vegetation and the shear stress resulting from the tidal flow in the creek, plays an important role in the hydrodynamics of the mangrove swamp.     

Fluxes of bacterioplankton between a tidal estuary and the sea: returning to the “Outwelling Hypothesis”

The tidal dynamics of bacterioplankton communities at the outer part ofa shallow estuary (Ria de Aveiro, Portugal) were studied during 6 tidal cyclesat a fixed sampling site. Bacterial numbers (0.2–8.1 ×10⁹ cells l^–1), aminopeptidase activity(189–1662 nmol l^–1 h^–1),-glucosidase activity (1.7–67.0 nmoll^–1 h^–1) and potential glucoseincorporation (0.48–3.99 nmoll^–1 h^–1) followed a consistent patternof increase during ebb and decrease during flood.Fluxes of bacterioplankton populations and associated heterotrophic activitiesbetween the estuary and the coastal area during a tidal cycle were estimatedfrom the water flux as derived from a two-dimensional vertically-integratednumerical model. The net fluxes estimated for a tidal cycle ranged from–26.0 to –2.5 to × 10¹⁶ bacterial cells. The nettidal fluxes of potential heterotrophic activities ranged from –10 to–80 mol h^–1 for aminopeptidase, –0.33to –1.10 mol h^–1 for -glucosidase and–0.18 to +0.03 mol h^–1 for glucoseincorporation. Net fluxes were generally negative in sign indicating thetransfer of phyto- and bacterioplankton, as well as potential capacities for thedegradation and recycling of organic matter, from the outer estuarinecompartment to the sea.     

Distribution of polychlorinated biphenyls (PCBs), lead,and cadmium in Manko Tidal Flat,Okinawa

Concentrations of polychlorinated biphenyls (PCBs), Pb, and Cd in sediment samples from the Manko Tidal Flat, an important area for migratory birds in Okinawa, were analyzed. High concentrations of PCBs were detected in the sediment samples from sites under a bridge at the end of the Manko Flat, whereas Pb and Cd concentrations did not indicate specific pollution. The spatial distribution and homologue proportion of PCBs indicated that these PCBs are probably attributed to the residue of paints used on the bridge in the 1970s. PCBs were detected in tilapias from sites in the Manko Flat and in a river connecting to the flat without head constructions. PCBs were also detected in small invertebrates, tanaids, in the flat. The distribution of PCB concentrations in the fauna was parallel to that in the sediments. The average PCB homologue proportions in tilapias and tanaids were similar to those in sediments.     

Submarine groundwater discharge in Osaka Bay, Japan

Submarine groundwater discharge (SGD) rates in Osaka Bay were continuously measured and analyzed to evaluate seawater–groundwater interactions. Fast Fourier transfer and power spectrum density methods were applied to analyze the dominant periods of the SGD variations. Diurnal and semidiurnal periods of SGD variation were found, and they were caused by tidal effects. According to the separation of SGD into fresh and recirculated water components using automated seepage meter measurements and terrestrial groundwater flow analyses, the fresh groundwater component in SGD was evaluated to be in the range 4%–29% at Tannowa, Osaka. Therefore, SGD rates depend mainly on the volume of recirculated seawater. Correlation analyses between SGD and sea level show that SGD is delayed by 4h after sea level changes.     

Consolidation and volumetric soil-water content of salt marsh soils following habitat modification for mosquito control

The runnelling form of habitat modification for mosquito control in saltmarsh increases tidal frequency, and may affect soil properties such as volumetric soil-water content and consolidation. The effects of habitat modification on soil properties are in turn likely to affect ecological processes. Runnels constructed mechanically to a depth of no more than 0.3 m with smooth, spoon shaped edges linked isolated mosquito-breeding pools in the high marsh to the tidal source at the saltmarsh/mangrove interface. The physical design of runnels may result in a significant increase in the frequency of flooding tidal events that flush isolated mosquito-breeding pools. Impacts of the runnelling technique were determined at three marshes using two sampling protocols: (a) comparisons between modified and unmodified shores and (b) comparisons with lateral distance from a runnel. At one marsh, volumetric water content was significantly higher at runnelled than at unrunnelled sites after tides that only partly inundated the marsh, but this pattern was not found at the other marshes. Soil consolidation was greater further from the shore, but was not different between runnelled and unrunnelled shores. Measurements at different lateral distances from runnels demonstrated higher water content levels and lower consolidation up to 5 m from runnels and no effect further away. The varied responses to runnelling at different marshes may reflect specific site characteristics such as slope and hydraulic tidal forces. Remedial strategies for similar mosquito control techniques, based on habitat modification, should include dynamic classifications of saltmarshes.     

温州湾灵昆岛东滩潮间带大型底栖动物群落的季节动态

潮间带是滩涂湿地生态系统的重要类型,由于处于海陆过渡地带,海陆环境因子的交替作用,物质交换过程复杂多变,因此潮间带底栖动物生态学的研究一直备受关注。国外的研究开展较为深入,如大型底栖动物在空白栖息地上定植过程及机制的研究,指出幼体成活率对定植存在决定性影响,探讨物种运动对滩涂大型底栖动物分布、多样性、密度和生物量在小尺度上的影响机制,     

浙江省某PCBs废物储存点对其邻近滩涂生态系统的毒性风险

在浙江省沿海某化工厂内含PCBs废物储存点邻近滩涂上设6个采样点,用GC-MS方法检测各采样点水样、滩涂泥样及大弹涂鱼样品中毒性最强的12种二噁英类PCB(DL-PCB)异构体的含量。结果表明,所有样品DL-PCBs检出率、样品单邻位异构体PCB118和非邻位异构体PCB81检出率均为100％,且PCB118和81的含量均与总DL-PCBs量有较好的相关性,在水样、泥样和鱼样品中,PCB118与总DL-PCBs含量的相关系数(r)分别为0.97、0.95和0.91,PCB81与总DL-PCBs含量的相关系数(r)分别为0.93、0.99和0.98。环境样品中以低氯异构体(PCB81和77)为主,而生物样品中高氯异构体(PCB118和105)含量较高。采样区域内大弹涂鱼从水体和泥土中的平均富集系数分别为392.54和14.03,且鱼体PCBs含量与沉积物中DL-PCBs浓度高度相关(r＝0.97)。在距堆场水沟入海口150 m内水体和沉积物中DL-PCBs含量已处于较高污染水平(分别大于599.34 ng/L和10.97 ng/g),且采样区域内大弹涂鱼PCBs含量(均大于59.19 ng/g脂重)显著高于其它地区。毒性当量研究表明,非邻位的PCB126和PCB169是样品总TEQs的主要贡献者,且所有水样和鱼样的TEQs都分别显著超过日本水环境限值1 pg TEQ/L和欧盟水产品标准值8 pg TEQ/g湿重(P<0.001);应用MacDonald沉积物毒性评价方法研究表明,1-4＃泥样已具有较高毒性风险。综合DL-PCBs含量和毒性当量分析表明,清挖4a后,该PCBs废物堆场仍对周边滩涂生态系统具有一定毒性风险,对人体健康存在潜在危害。     

漩门湾围垦区外滩涂不同生境大型底栖动物功能群及其变化

为研究围垦后滩涂湿地不同生境中大型底栖动物的功能群及其变化,于2010年10月至2012年7月在漩门湾围垦区外滩涂湿地3种生境进行了8个季度的大型底栖动物采样调查。3种生境各选2条与海岸线垂直的带状断面,各断面布设5个样点,每个样点均选取4个样方,用定量采样器采集泥样。两周年定量采集共获得大型底栖动物49种,隶属5门5纲29科。依据食性类型将底栖动物划分为浮游生物食者(Planktophagous group,Pl)、植食者(Phytophagous group,Ph)、肉食者(Carnivorous group,C)、杂食者(Omnivorous group,O)和碎屑食者(Detritivorous group,D)5个功能群。结果表明,互花米草草滩(HH)各功能群的物种数分别为6、10、13、6、5种,共计40种;自然光滩(GT)分别为4、8、12、11、6种,共计41种;红树林泥滩(HS)分别为5、8、12、7、4种,共计36种。两周年3种生境内Pl和Ph始终为主导功能群,其密度和生物量均较高,且平均密度和平均生物量均是PlPh。对两周年各生境功能群的多样性指数(Margalef丰富度指数、Shannon-Wiener多样性指数以及Pielou均匀度指数)进行无重复双因素方差分析表明:两周年中3种多样性指数在生境间均无显著性差异;两周年中S在功能群间均有极显著差异,第1周年H'、J在功能群间均无显著性差异,第2周年H'有极显著差异,J有显著差异。     

Benthic fauna in tropical tidal flats – a comparative perspective

Tidal flats extend seaward from mangrove forests along many tropicalcoastlines. This contribution compiles the current knowledge on tropicaltidal flats with regard to species richness, abundance, spatial distributionpatterns and ecological roles taken by major organisms. Tidal flatsencompass a variety of soft-sediment habitats which are inhabited by aspecies-rich fauna. Species numbers are generally higher than in temperatetidal flats, but vary widely between tropical sites where they have not yetbeen fully assessed due to lack of research and taxonomic problems. Theassessment of biodiversity is further complicated by a low species frequency,the small size of macroinfaunal organisms and variations in the occurrence ofspecies between sites. Mean abundance ranges from 1000–2000individuals m^-2, although figures ten times higher have beenrecorded in a mudflat in Costa Rica, and there are great variations in general.Individual densities of small-sized macrofauna are about ten times higher than for larger macrobenthos. A generalized zonation scheme for intertidaldistribution patterns of tropical tidal flat fauna is presented. The comparisonshows that the occurrence of macrofauna and especially of ecosystemengineers varies between sites, which can in turn explain the great variabilityin species abundance patterns recorded in benthic surveys of tidal flatswithin and between regions. This review revealed similarities as well asdifferences between various tropical tidal flats, which underlines the need for further comparative studies to be done, using the same methodology, before generalizations can be made.