Assembly processes in upper subtidal macroalgae: The effect of wave exposure

The structure and diversity of sixteen macroalgal assemblages originating from two coastal locations in the Northern (Kavala gulf) and Central (Maliakos gulf) Aegean in Greece were explored by examining their relative abundance distributions (RADs) and fitting five stochastic niche-based models. A mechanistic interpretation of the underpinning assembly processes was attempted by relating the assumptions of the fitted models with available abiotic data corresponding to each assemblage. The random fraction niche-based model, assuming a random niche apportionment to species, was fitted to the majority of Maliakos assemblages characterized by more evenly distributed and speciose RADs, whereas the random assortment model, assuming no relationship among species abundance and niche size, was fitted to most of the Kavala assemblages characterized by steeper RADs with fewer species. Among the possible underlying mechanisms, wave exposure seems to play a key role in macroalgal assembly processes; however factors such as biogeography and hard substrate availability must be also taken into consideration. Short-term processes as changes in resource availability (nutrients and light), known as drivers of assembly rules in other primary producers (e.g. phytoplankton), do not considerably affect macroalgae in the oligotrophic Eastern Mediterranean, possibly due to their longer life spans.     

Mesoscale eddies dominate surface phytoplankton in northern Gulf of Alaska

The HNLC waters of the Gulf of Alaska normally receive too little iron for primary productivity to draw down silicate and nitrate in surface waters, even in spring and summer. Our observations of chlorophyll sensed by SeaWiFS north of 54°N in pelagic waters (>500 m depth) of the gulf found that, on average, more than half of all surface chlorophyll was inside the 4 cm contours of anticyclonic mesoscale eddies (the ratio approaches 80% in spring months), yet these contours enclosed only 10% of the total surface area of pelagic waters in the gulf. Therefore, eddies dominate the chlorophyll and phytoplankton distribution in surface pelagic waters. We outline several eddy processes that enhance primary productivity. Eddies near the continental margin entrain nutrient - (and Fe) - rich and chlorophyll-rich coastal waters into their outer rings, advecting these waters into the basin interior to directly increase phytoplankton populations there. In addition, eddies carry excess nutrients and iron in their core waters into pelagic regions as they propagate away from the continental margin. As these anticyclonic eddies decay, their depressed isopycnals relax upward, injecting nutrients up toward the surface layer. We propose that this transport brings iron and macro-nutrients toward the surface mixed layer, where they are available for wind-forced mixing to bring them to surface. These mesoscale eddies decay slowly, but steadily, perhaps providing a relatively regular upward supply of macro-nutrients and iron toward euphotic layers. They might behave as isolated oases of enhanced marine productivity in an otherwise iron-poor basin. We note that much of this productivity might be near or just below the base of the surface mixed layer, and therefore poorly sampled by colour-sensing satellites. It is possible, then, that eddies enrich phytoplankton populations to a greater extent than noted from satellite surface observations only.     

Topographic Rossby waves in the Gulf of Mexico

Observations of topographic Rossby waves (TRW), using moored current meters, bottom pressure gauges, and Lagrangian RAFOS floats, are investigated for the deep basin of the Gulf of Mexico. Recent extensive measurement programs in many parts of the deep gulf, which were inspired by oil and gas industry explorations into ever deeper water, allow more comprehensive analyses of the propagation and dissipation of these deep planetary waves. The Gulf of Mexico circulation can be divided into two layers with the ∼800-1200 m upper layer being dominated by the Loop Current (LC) pulsations and shedding of large (diameters ∼300-400 km) anticyclonic eddies in the east, and the translation of these LC eddies across the basin to the west. These processes spawn smaller eddies of both signs through instabilities, and interactions with topography and other eddies to produce energetic surface layer flows that have a rich spectrum of orbit periods and diameters. In contrast, current variability below 1000 m often has the characteristics of TRWs, with periods ranging from ∼10-100 days and wavelengths of ∼50-200 km, showing almost depth-independent or slightly bottom intensified currents through the weakly stratified lower water column. These fluctuations are largely uncorrelated with simultaneous upper-layer eddy flows. TRWs must be generated through energy transfer from the upper-layer eddies to the lower layer by potential vorticity adjustments to changing depths of the bottom and the interface between the layers. Therefore, the LC and LC eddies are prime candidates as has been suggested by some model studies. Model simulations have also indicated that deep lower-layer eddies may be generated by the LC and LC eddy shedding processes.In the eastern gulf, the highest observed lower-layer kinetic energy was north of the Campeche Bank under the LC in a region that models have identified as having strong baroclinic instabilities. Part of the 60-day TRW signal propagates towards the Sigsbee Escarpment (a steep slope at the base of the northern continental slope), and the rest into the southern part of the eastern basin. Higher energy is observed along the escarpment between 89°W and 92°W than either under the northern part of the LC or further south in the deep basin, because of radiating TRWs from the western side of the LC. In the northern part of the LC, evidence was found in the observations that 20-30-day TRWs were connected with the upper layer through coherent signals of relative vorticity. The ∼90° phase lead of the lower over the upper-layer relative vorticity was consistent with baroclinic instability. Along the Sigsbee Escarpment, the TRWs are refracted and reflected so that little energy reaches the lower continental slope and a substantial mean flow is generated above the steepest part of the escarpment. RAFOS float tracks show that this mean flow continues along the escarpment to the west and into Mexican waters. This seems to be a principal pathway for deepwater parcels to be transported westward. Away from the slope RAFOS floats tend to oscillate in the same general area as if primarily responding to the deep wave field. Little evidence of westward translating lower-layer eddies was found in both the float tracks and the moored currents. In the western gulf, the highest deep energy levels are much less than in the central gulf, and are found seaward of the base of the slope. Otherwise, the situation is similar with TRWs propagating towards the slope, probably generated by the local upper-layer complex eddy field, being reflected and forcing a southward mean flow along the base of the Mexican slope. Amplitudes of the lower-layer fluctuations decay from the northwest corner towards the south.     

“纳沙”台风引起北部湾沿岸风暴射流及其机制

基于FVCOM模式建立一个三维数值模型,对2011年“纳沙”台风登陆北部湾前后水位与流场变化进行了分析,并探究了风暴射流的生成机制。结果表明,广西近岸风暴射流的产生是对台风到来造成的水位起伏变化的一种正压响应;台风进入到北部湾期间,造成北部湾近岸水位先降低后升高,所导致的水位梯度差产生了驱动力,促使海水向西运动增强,从而导致在广西近海风暴射流的产生;台风登陆期间琼州海峡西向流流量增大到0.4 Sv以上,最大可达0.7 Sv;台风进入到北部湾后,促使琼州海峡西向流更多进入到北部湾,造成湾内正位涡输入增大,产生了气旋式环流来维持位涡平衡,同时气旋式环流也有利于向西运动的风暴射流增强;流经广西沿岸的风暴射流引起向西的水体输运可达0.2 Sv,对北部湾内营养盐以及污染物运移将产生重要影响。     

The Influence of Physical Factors on the Variation of Phytoplankton and Nutrients in the Bohai Sea

The cycle of the phytoplankton in a coastal water is controlled by the biological processes, solar radiation, water temperature and physical transport processes. A three-dimensional ecosystem dynamic model is adopted in this study to investigate the influence of different physical factors on the variation of phytoplankton and nutrients in the Bohai Sea. The simulation is carried out for the year 1982. The simulated annual cycle of the primary production and nutrients are in reasonable agreement with the observations in the pattern. Vertical mixing can both affect the vertical transportation of nutrients and horizontal distribution of primary production. In winter the vertical distribution of nutrients is homogeneous because of the intensive mixing, while in summer there is a high value of nutrients in the depth about 15 m due to the stratification. The high primary production plague and the weak mixing center is positional correspondence. The production of phytoplankton is sensitive to the photosynthetically active radiation, which is strongly influenced by the transparency. The increase of the transparency can promote the production in spring and autumn significantly, but has little effect on the production in summer. The change of the transparency can both affect the occurrence time and the amplitude of the phytoplankton bloom dramatically. Horizontal advection does not affect the variation trend of the annual cycle of chlorophyll-a, but does affect the relative magnitude of the phytoplankton bloom, especially in summer. Horizontal advection can dramatically alter the horizontal distribution of chlorophyll-a. The maximum concentration of chlorophyll-a without horizontal advection in summer is twice as high than that with advection and the high chlorophyll-a areas locate along the coast. The river discharge only has regional influence on the ecosystem. The Huanghe River with high nitrate concentration influ-ences the annual cycle of nitrogen of the Laizhou Bay significantly.     

Global cyclostratigraphy: a model of carbonate growth patterns

Cyclostratigraphy is the study of cyclic depositional patterns produced by climatic and tectonic processes. A global-scale quantitative cyclostratigraphic model is described which simulates carbonate growth patterns controlled by tectonic and climatic processes. The model uses seven factors simulating the effects of physical and chemical environments on the deposition rates of carbonate accumulations. These factors are sea-level change, the rate of basement subsidence, food supply (influence of nutrients), available sunlight, temperature, salinity and dissolved oxygen. The factors are considered as functions of climatic and tectonic processes. The model also integrates Milankovitch-induced short-term climatic changes with the long-term tectonic evolution of basins to examine the potential carbonate accumulation patterns. The two-dimensional computer model results provided here show that: (1) carbonate growth patterns in different climates and under different tectonic processes can be modelled quantitatively; (2) carbonate production increases towards the equator (decreasing latitude) as the temperature and nutrition supply increase in tropical belts, and production changes because of expansion or contraction of the tropical belt in different climatic periods; (3) when matched with the turbidity, the model describes different carbonate accumulation patterns in different climatic patterns; (4) at either abnormally high or low salinity, carbonate accumulation rates decline sharply, and the salinity becomes normal away from the strand line; and (5) cyclic sea-level changes cause a cyclic change of carbonate accumulation. A case study is presented from the Upper Pennsylvanian of Texas. The simulation results indicate that carbonate growth patterns observed from field, well or seismic data are accurately modelled by the quantitative procedure given here.     

Impacts of anthropogenic activities on the Changjiang(Yangtze)estuarine ecosystem(1998–2012)

Estuarine ecosystem has greatly changed in the recent decades due to anthropogenic perturbations in the Changjiang Estuary. Change patterns and impact factors were analyzed based on the continuous data...     

珠江口淇澳岛红树林区海水中营养盐和叶绿素a研究初探

2004年4月对珠江口淇澳岛红树林区进行现场调查,分析该区域营养盐和叶绿 素a浓度分布特征,并对两者之间的相关性进行探讨,研究结果表明该区域营养盐及 叶绿素a浓度均较高;而且靠近岛屿、红树植物分布较多的区域,溶解无机氮(DIN) 含量要低于距离岛屿较远、红树植物较少的区域;相关性分析表明叶绿素a与无机氮 化合物之间相关性较好,与磷(PO4-P)、硅(SiO3-Si)之间却无明显相关,说明无机氮 化合物与浮游植物和初级生产力之间关系密切,氮元素及其循环对红树林生态系统 可能起着重要的作用．     

Quaternary evolution of the Gulf of İzmit (NW Turkey): a sedimentary basin under control of the North Anatolian Fault Zone

The Quaternary evolution of the Gulf of İzmit, situated on the tectonically active North Anatolian Fault Zone (NAFZ), was investigated using seismic reflection, paleontologic, and sediment textural data. On the basis of seismic stratigraphic and sedimentologic-paleontologic interpretations, four depositional units were distinguished within the Plio-Quaternary sequence of the Gulf of İzmit. According to these data, Plio-Quaternary deposits supplied from the northern terrestrial area started to accumulate during a progradational phase, in a south-facing half-graben. A coarse-grained sedimentary unit prograding into the gulf from the south since 200 ka b.p. indicates a dramatic variation in the evolution of the gulf, with the initiation of a new strike-slip fault of the NAFZ and a corresponding uplift of the Armutlu Peninsula in the south of the gulf. During the evolution of this fault from a wide shear zone consisting of right-stepped strike-slip faults and pull-apart basins to a localized principal fault zone, sediments were deposited under the influence of northerly prograding terrestrial and shallow-marine conditions due to relative sea-level fluctuations in the Marmara Sea. During this period, the Gulf of İzmit was invaded mainly by Mediterranean and partly by Black Sea waters. In the latest glacial period, shallow areas in the gulf became subaerially exposed, whereas the central and western sub-basins of the gulf turned into lakes. The present evolution of the Gulf of İzmit is controlled by the after effects of the new rupture of the NAFZ and the estuarine nature of the gulf environment.     

Quantifying cross-shelf and vertical nutrient flux in the Coastal Gulf of Alaska with a spatially nested,coupled biophysical model

The Coastal Gulf of Alaska (CGOA) is productive, with large populations of fish, seabirds, and marine mammals; yet it is subject to downwelling-favorable coastal winds. Downwelling regions in other parts of the world are typically much less productive than their upwelling counterparts. Alternate sources of nutrients to feed primary production in the topographically complex CGOA are poorly known and difficult to quantify. Here we diagnose the output from a spatially nested, coupled hydrodynamic and lower trophic level model of the CGOA, to quantify both horizontal and vertical nutrient fluxes into the euphotic zone. Our nested model includes both nitrogen and iron limitation of phytoplankton production, and is driven by a fine-scale atmospheric model that resolves the effects of local orography on the coastal winds. Results indicate significant “rivers” of cross-shelf nitrogen flux due to horizontal advection, as well as “fountains” of vertical transport over shallow banks due to tidal mixing. Using these results, we constructed a provisional budget of nutrient transport among subregions of the CGOA. Contrary to expectations, this budget reveals substantial upwelling of nutrients over major portions of the shelf, driven by local wind-stress curl. These effects are large enough to overwhelm the smaller downwelling flux at the coast throughout the growing season. Vertical mixing by winds and tides, and horizontal flux from the deep basin, are other substantial contributors to nutrients above the 15-m horizon. These findings help to explain the productivity of this coastal ecosystem.     

Characterization of the Seasonal Circulation Patterns and Its Application on Oil Spill Transport in the Northwestern Continental Shelf of India

We implemented the Princeton Ocean Model to study the seasonal circulation patterns in the Gulf of Khambhat and surrounding oceans on the northwestern continental shelf of India. Simulated currents are used in General NOAA Operational Modeling Environment to track a past oil spill event in this region. The model's performance is evaluated against the Synthetic Aperture Radar (SAR) and in situ measurements. Mean currents, computed by subtracting tidal components from the simulated currents, are used together with satellite images of Chlorophyll-a to describe spatial patterns of the circulation. Mean-flow patterns inside the gulf are characterized with strong along-channel flow during southwest monsoon and spring seasons, which are weak during winter and autumn seasons. On the proximity of the gulf mouth currents are northwestward throughout the year except the southwest monsoon when the circulations are southwestward. Coastal boundary currents parallel to the 60 m isobath are prominent during the inter-monsoon and weak during the monsoon periods. Slope currents, near the shelf-break, are strong during southwest monsoon and spring periods. Numerical experiments suggest that ocean current is the main driver of the net transport of spilled oil in this region and other factors such as direct wind drift play negligible role.     

Distribution and vertical dynamics of planktonic communities at Sofala Bank, Mozambique

Coastal ecosystem processes are largely influenced by the interaction of different factors operating at various temporal and spatial scales, specifically those responsible for primary production patterns that modulate zooplankton and subsequent trophic levels. Hydrological processes, such as tidal cycles and coastal currents, nutrients availability, phytoplankton groups (studied through algal pigment signatures analysed by HPLC), and zooplankton abundance and distribution were investigated at the Sofala Bank (Mozambique), with special emphasis on their horizontal distribution and vertical dynamics (48 h). Horizontal distribution has shown inshore–offshore gradients in all analysed parameters, as well as inshore waters intrusion probably related to Zambezi River delta runoff. Tidal currents were responsible for major hydrological vertical variations and for horizontal and vertical advection of phytoplankton biomass in the surface and deepest layers, respectively. Nutrient concentrations were typical from oligotrophic regions, and nutrient ratios were strongly influenced by depleted nitrate + nitrite concentrations, indicating low estuarine discharges typical from the dry season. The very low N:P ratio obtained suggests strong nitrogen limitation to phytoplankton communities, supporting the low phytoplankton abundance observed. Both phytoplankton pigments and zooplankton were found mainly near the bottom (40 m depth), despite the latter displayed vertical migrations triggered by light variations. Phytoplankton community was dominated by microflagellates, specifically prymnesiophyceans, and behaved as a whole, except Cyanobacteria that displayed vertical distribution movements different from other phytoplankton groups, being mainly concentrated at mid-water column depths (10–20 m). This investigation enhances physico-chemical phenomena and their importance determining the planktonic communities vertical dynamics at Sofala Bank, a tropical coastal ecosystem of the Western Indian Ocean where planktonic dynamics are still poorly described and understood.     

Exposed sandy beaches as semi-closed ecosystems

On the basis of various lines of evidence, mostly coming from exposed sandy beaches in Southern Africa, it is postulated that under certain conditions high energy sandy beaches and their adjacent surf zones may function as viable ecosystems. Where surf zones are reasonably broad and shallow, cellular circulation patterns predominate and these tend to retain nutrients generated by the macrofauna and interstitial fauna of the beach. These nutrients may then cause blooms of surf zone phytoplankton which in turn serve as food for macrofauna filter feeders. With the perimeter of the circulation cells of the surf zone forming its marine boundary, the beach and surf zone may together be considered an ecosystem with surf phytoplankton the primary producers, beach macrofauna the consumers and interstitial fauna the decomposers.     

基于剖分的中尺度海洋温度场三维显示技术

针对网格化和数据量庞大的中尺度海洋标量场数据在其三维可视化中表现出来的构造效率较低和表达连续性效果较差的问题,以剖分重构为核心思想,采用三线性插值算法对数据进行加密处理,基于不同角度平面对温度场进行剖分和色彩映射,最后采用OpenSceneGraph图像渲染引擎的颜色、光照、透明度和回调等渲染技术展现更为真实的、科学的动态三维温度场,提供一种简洁、高效、科学的中尺度海洋温度场表达方法。     

The morphology and evolution of tidal sand bodies in the macrotidal Gulf of Khambhat,western India

Tidal sand bars and tidal sand ridges are extensively developed in the macrotidal Gulf of Khambhat, offshore western India. The inner and outer regions of the gulf are characterised by the development distinct tidal sand bodies with discrete geometries and dimensions. The outer gulf ridges are long, narrow, curvilinear and several metres high (∼20 m). They are asymmetric in cross-section and migratory in nature, forming ‘ribbon’ like sand bodies separated by tidal channels. Active dunes on these ridges indicate the presence of sand and their orientation parallel to palaeo-shorelines supports a tidal origin. In contrast to the outer gulf tidal sand ridges, sand bars associated with macrotidal estuaries flanking the Gulf of Khambhat typically have an elongate to diamond shape and are only hundreds of metres in width and a few kilometres length. These tidal sand bars occur in the estuary mouths and within the tidally influenced fluvial reaches of the rivers flowing into the gulf. The height of these sand bars is in the range ∼1–3 m. Due to high tidal ranges and bi-directional flow the sand bars do not develop significant height and are formed between the mutually evasive ebb and flow channels. Their bi-directional foresets and the presence of abundant mud drapes associated with the dunes within in-channel sand bars indicate a tidal origin.The Gulf of Khambhat acquired the present configuration in the last few thousand years since the Pleistocene sea-level lowstand (last glacial maximum, ∼18 ka) when the entire continental shelf was subaerially exposed and rivers down-cut into the coastal plain. With increasing sea-level rise, the exposed shelf was drowned, flooding parts of the Modern western Indian peninsula, and large tidal sand ridges formed in the outer gulf. After the fall of sea-level at 2 ka the gulf acquired the Modern configuration with multiple estuaries on both coastlines, rivers supplied the embayment with sandy sediment, and tidal sand bars formed in the Modern estuaries.Quantitative data gathered from the Modern Gulf of Khambhat indicates that for the P50 case, a vertical drill hole will encounter tidal sand bodies (ridges and bars combined) of approximate dimensions 1700 m long, 470 m wide and 1.5 m high, with a spacing of 400 m. In subsurface hydrocarbon reservoirs, where data is sparse and only limited amount of core is available, this quantitative dataset can be useful to constrain subsurface geocellular models. Also, the overall geometry, distribution and aspect ratio of the tidal sand ridges and tidal sand bars can be used to identify ancient counterparts through seismic geomorphology or in core.     

Phosphorus and nitrogen cyclings in the pelagic system of hiroshima bay: Results of numerical model simulation

A numerical ecosystem model expressing both phosphorus and nitrogen cyclings in the pelagic system of Hiroshima Bay, Japan, was developed in order to investigate the seasonal variations of these elements and their annual budgets. Based on the geophysical and chemical structures of the bay, Hiroshima Bay was divided into northern and southern boxes, themselves divided into two layers of an upper 5 m and a lower layer according to the stratification of the water column. The model consists of equations representing all relevant physical and biological processes. The results revealed that the internal regeneration of materials was an important source of bioavailable nutrients for phytoplankton growth in the water column. The incorporation of phytoplankton aggregation improved the accuracy of the outputs in comparison to the observed data, especially during the stratified summer season. The results also indicated that phosphorus limitation of phytoplankton growth occurs in the upper layer during summer while light limitation occurs in the lower layer. In addition, physical processes such as diffusion and advection were also important as they ensured that most of regenerated nutrients in the lower layer were transported to the upper layer. Thus, these processes might support the high primary production and the production of oysters that are extensively cultured in this bay. Considering the informative results obtained, the model used in this study provides a sound basis and tool to describe the dynamics of phosphorus and nitrogen cyclings in Hiroshima Bay.     

Associational resistance mediates predator--prey interactions in a marine subtidal system

There is a growing awareness of the role that indirect interactions play in influencing food webs and ecosystem structure. In this study, the hypothesis that crustose algal epibionts provide gastropods associational resistance from predation was investigated through field surveys and laboratory feeding assays. In rocky low intertidal/shallow subtidal systems in the northeast Pacific, several species of crustose algae (the red alga Peyssonnelia meridionalis and crustose corallines) can colonize the shells of living Tegula brunnea snails. The growth patterns of these epibiontic crustose algae allow them to cover their host’s surface completely, which may, in turn, protect their hosts from predation. A multi‐site field survey of T. brunnea revealed that >60% of snails were at least 75% covered with one or more species of crustose algae, with 35% fully covered, indicating that this is common in the field. Laboratory feeding assays revealed that sea stars, a primary predator of T. brunnea, distinguished among snails with different shell coverings; Pisaster consumed nearly three times as many bare (i.e. no crustose algae) snails as those covered with Peyssonnelia, while Pycnopodia consumed four times as many bare snails as those covered with crustose corallines. These results suggest that epibiont crustose algae can benefit their hosts via associational resistance; this finding may have implications for the role of associational resistance in trophic interactions.     

Waves,long waves and nearshore morphology

Recent field measurements on beaches of different slopes have established that wave motion at periods substantially longer than the incident waves dominates the velocity field close to the shore. Analysis of a number of extensive data sets shows that much of this long wave motion is in the form of progessive edge waves, though forced wave motion, standing edge waves and free waves propagating away from the shore may also contribute to the energy.Theoretically, the drift velocities in bottom boundary layers due to edge waves show spatial patterns of convergence and divergence which may move sediment to form either regular crescentic or cuspate features when only one edge wave mode dominates, or a bewildering array of bars, bumps and holes when several phase-locked modes exist together.Convincing field demonstration of the link between nearshore topography and edge waves only exists for the special case of small-scale beach cusps on steep beaches, formed by edge waves at the subharmonic (twice the period) of the incident waves. At longer periods the link is proving more difficult to establish, due to the longer time-scales of topographic changes, the interaction between pre-existing topography and the water motion, and the observation of broad-banded edge wave motion which is not readily linked to topography with a well-defined scale.These ideas are, however, central to the study of nearshore processes, as most of the plausible alternate hypotheses do not seem to lead to quantitative predictions. Clearly, further theoretical and observational work is essential.     

Biogeochemical responses to the removal of maricultural structures from an eutrophic lagoon (Tapong Bay) in Taiwan

The biogeochemistry of Tapong Bay, one of the major lagoons in southern Taiwan, was studied from 1999 to 2004, encompassing a period in 2003 in which aquaculture activities were terminated and the associated structures removed. Removal of the maricultural structures resulted in the reduction of the mean time for water exchange time in Tapong Bay from about 10+/-2d to 6+/-2d. The annual mean concentration of measured nutrients (DIN, DIP and DSi) also decreased significantly, likely due to improved water exchange, ceased feeding and increased biological utilization. An overall high primary production was maintained and likely to be constrained by temperature, light availability and turbidity rather than by abundant nutrients throughout the study period. The change in stoichiometric ratios among inorganic and organic nutrients (C/N, Si/N, N/P) may be attributed to the shift of plankton community between the two periods. The annual mean of Delta POC/Delta PON was 8.1, a little bit larger than that (7.3) before removal, also possibly resulting from the shift of planktonic community (from diatom-dominated to flagellate-dominated and increase of total phytoplankton and zooplankton) and removal of periphyton and oysters. The Tapong Bay shows a 37% increase (from 5.6 to 7.7 mol C m(-2)yr(-1)) in net ecosystem production (NEP) after structure removal, although the increase was not statistically significant. The change in environmental conditions has therefore influenced profoundly the carbon and nutrient biogeochemical processes and budgets in the semi-enclosed ecosystem.