Tidal transport and dispersal of marine toxic microalgae in a shallow, temperate coastal lagoon

A numerical model was used to predict toxic microalgal transport and dispersion in Ria de Aveiro in Portugal. A previously developed Lagrangean particle tracking model coupled to a calibrated two-dimensional hydrodynamic model of Ria de Aveiro was used. Microalgae were regarded as passive particles and the methodology used allowed the determination of their trajectories, as induced by the tidal currents predicted by the hydrodynamic model. The model assumes Ria de Aveiro as vertically homogeneous and does not take into account the vertical distribution patterns of microalgae. Simulations were carried out during extreme spring and neap tides, with microalgal released at the mouth of the lagoon at the local flood. The maximum and minimum areas affected during the occurrence of toxic microalgal blooms were estimated to evaluate the suitability of the distribution of the sampling stations included in the local monitoring program. It was found that the tidal currents greatly determine the microalgal horizontal distribution and dispersal in the lagoon. The results confirmed that the locations of water and bivalve shellfish sampling stations, postulated by INIAP/IPIMAR, in the context of the local harmful algal bloom (HAB) program, were appropriate, although some possible refinements were identified.     

Hydrological characterisation of Ria de Aveiro,Portugal, in early summer

The hydrological features of Ria de Aveiro, a coastal lagoon on the northwest Atlantic coast of Portugal, were investigated in two sampling surveys carried out between 3/6 and 24/6/97 and between 29/6 and 7/7/97, respectively. There was a significant freshwater inflow into the lagoon during the first survey, especially in the first days, due to the recent rainfalls. Records concerning water level, salinity, temperature and current velocity were performed at several stations located along the four main channels of the lagoon. The type of tide at the mouth was determined and was observed that astronomical tide is the main forcing agent driving water circulation in Ria de Aveiro. The tide at the mouth is semidiurnal and the tidal wave propagation in the lagoon has the characteristics of a damped progressive wave. Typical estuarine longitudinal salinity and temperature gradients connected with the distance to the mouth were identified, whereas vertical and transverse gradients were found unimportant, except in the frontal zone between oceanic and fresh water masses. According to the results, even though Ria de Aveiro should be considered as vertically homogeneous, some channels may reveal characteristics of a partially mixed estuary, depending on the freshwater input.     

High-resolution seismic imaging of gas accumulations and seepage in the sediments of the Ria de Aveiro barrier lagoon (Portugal)

Methane is a powerful greenhouse gas and an important energy source. The global significance and impact in coastal zones of methane gas accumulation and seepage in sediments from coastal lagoon environments are still largely unknown. This paper presents results from four high-resolution seismic surveys carried out in the Ria de Aveiro barrier lagoon (Portugal) in 1999, 2002 and 2003. These comprise three chirp surveys (RIAV99, RIAV02, RIAV02A) and one boomer survey (RIAV03). Evidence of extensive gas accumulation and seepage in tidal channel sediments from the Ria de Aveiro barrier lagoon is presented here for the first time. This evidence includes: acoustic turbidity, enhanced reflections, acoustic blanking, domes, and acoustic plumes in the water column (flares). The stratigraphy and structural framework control the distribution and extent of gas accumulations and seepage in the study area. In these shallow systems, however, tidal altitude variations have a significant impact on gas detection using acoustic methods, by changing the raw amplitude of the enhanced seismic reflections, acoustic turbidity, and acoustic blanking in gas-prone areas. Direct evidence of gas escape from drill holes in the surrounding area has shown that the gas present in the Ria de Aveiro consists of biogenic methane. Most of the gas in the study area was probably generated mainly in Holocene lagoon sediments. Evidence of faults affecting the Mesozoic limestones and clays underlying some of the shallow gas occurrences, and the presence of high-amplitude reflections in these deeper units raise the possibility that some of this gas could have been generated in deeper sedimentary layers, and then migrated upward through the fractured Mesozoic strata.     

Effect of low salinity on the survival of recently hatched veliger of Nassarius reticulatus (L.) in estuarine habitats: A case study of Ria de Aveiro

The effect of low salinity on the survival of recently hatched veliger of the gastropod Nassarius reticulatus (L.) was studied under laboratory conditions at 17 °C ± 1 °C. Significant mortality occurred for salinities ≤ 17 psu and the LS₅₀ (salinity that causes 50% mortality) varied from 14.5 psu to 17.2 psu for exposures between 1 h and 48 h, respectively. The results were included in a mathematical model in order to estimate the mortality of N. reticulatus veliger in Ria de Aveiro under different salinity scenarios determined by numerical simulation. The model predicts a massive mortality of veliger immediately after their eclosion (1 h) in Ria de Aveiro during spring tide when the river input reaches its expected maximum — a situation that has been observed occasionally and may overlap a massive eclosion of veliger in the water. Except in this extreme situation, the mortality in Ria de Aveiro is generally restricted to the upstream limits of the channels. The results indicate that N. reticulatus recruitment in estuaries may strongly depend on the prevailing salinity regime.     

Nutrient dynamics and seasonal succession of phytoplankton assemblages in a Southern European Estuary: Ria de Aveiro, Portugal

The spatial and temporal dynamics of dissolved inorganic nitrogen, dissolved phosphate, dissolved silica and chlorophyll a were measured seasonally at eight stations in the Ria de Aveiro. Between December 2000 and September 2001, the seasonal succession of phytoplankton assemblages, inferred after the spatial and seasonal variation of silica and of chlorophyll a concentrations, showed that diatoms (μmol Si L⁻¹) dominated from late autumn until early spring, while chlorophytes (μg Chl a L⁻¹) bloomed during late spring and summer. The Si:N:P ratios and Si concentrations indicated no seasonal depletion in dissolved silica, as in other temperate systems, possibly because of abnormal precipitation and flood events prolonging the supply of dissolved Si to the system. The Si:N:P ratios suggested P limitation at the system level. Despite the relative proportions of available nutrients, the mean phosphorus concentration (5.3 μmol L⁻¹) was above the reported half-saturation constants for P uptake by phytoplankton. Thus, in Ria de Aveiro, the seasonal succession of phytoplankton assemblages may also be dependent on the grazing capacity of the pelagic community through top-down regulation.     

Evaluation of the ecological effects of heavy metals on the assemblages of benthic foraminifera of the canals of Aveiro (Portugal)

Aveiro is a town with 80,000 inhabitants situated in the central west coast of Portugal. It is located at the centre of the Ria de Aveiro, a coastal lagoon that functions as a multi-estuarine area. This town is crossed by several canals which are connected with lagoon channels through canal locks. The operation of the canal locks influences the hydro dynamism in Aveiro's canal and this and other human activities have left a sedimentary record. The study of these records was based on the sediments grain size and composition, mineralogy (by XRD techniques), geochemical (by ICP-MS), total organic carbon (TOC), and microfaunal (benthic foraminifera) content in 15 grab-samples collected in 2006 in Aveiro's canal. The total elemental concentrations evaluated by total digestion of the sediment fraction <2000 μm revealed the presence of “hot spots” of pollution caused by heavy metal contaminants in some Aveiro canals, related to legacies of past industrial activities. These “hot spots” have, for instance, higher available concentrations of Al, Cd, Co, Cu, Fe, Pb, Mn and Zn (evaluated by sequential chemical extractions) and are located in Paraíso, Alboi, Botirões and Cojo Canals, at sites where the sediments are finer and richer in TOC. Abiotic and biotic variables submitted to principal component analysis and cluster analysis highlights the hydrodynamics and human effects on the system and the negative influence of pollutants on the benthic organisms (foraminifera).     

Inputs of organic carbon from Ria de Aveiro coastal lagoon to the Atlantic Ocean

Land/ocean boundaries constitute complex systems with active physical and biogeochemical processes that affect the global carbon cycle. An example of such a system is the mesotidal lagoon named Ria de Aveiro (Portugal, 40°38′N, 08°45′W), which is connected to the Atlantic Ocean by a single channel, 350 m wide. The objective of this study was to estimate the seasonal and inter-tidal variability of organic carbon fluxes between the coastal lagoon and the Ocean, and to assess the contribution of the organic carbon fractions (i.e. dissolved organic carbon (DOC) and particulate organic carbon (POC)) to the export of organic carbon to the Ria de Aveiro plume zone. The organic carbon fractions fluxes were estimated as the product of the appropriate fractional organic carbon concentrations and the water fluxes calculated by a two-dimensional vertically integrated hydrodynamic model (2DH). Results showed that the higher exchanges of DOC and POC fractions at the system cross-section occurred during spring tides but only resulted in a net export of organic carbon in winter, totalling 85 t per tidal cycle. Derived from the winter and summer campaigns, the annual carbon mass balance estimated corresponded to a net export of organic carbon (7957 = 6585 t yr⁻¹ POC + 1372 t yr⁻¹ DOC). On the basis of the spring tidal drainage area, it corresponds to an annual flux of 79 g m⁻² of POC and 17 g m⁻² of DOC out of the estuary.     

The dynamic behaviour of a river-dominated tidal inlet, River Murray, Australia

Australia's largest river, the River Murray, discharges to the southern ocean through a coastal lagoon and river-dominated tidal inlet. Increased water extractions upstream for irrigation have led to significantly reduced flows at the mouth and, as a result, the area is undergoing rapid change, particularly with regard to the rate at which sediment is being transported into the lagoon. Based on detailed and accurate bathymetric surveys it has been possible to estimate that the rate of lagoon in-filling is of the order of 100,000 m³ per year for the period June 2000 to May 2003, although the actual rate shows significant year to year variability. Dredging of the lagoon commenced in 2000 in an attempt to reverse the trend.In an effort to understand the behaviour of the inlet a one-dimensional numerical model of the inlet has been developed. The model extends the original of van de Kreeke by including a dynamic inlet throat area based on predicted river flows and a sediment transport module to predict the resulting net sediment transport. Comparisons with water level data collected on both the ocean and lagoon sides of the mouth have shown that the model is able to predict the attenuation and lag of the tidal signal reasonably well. The sediment transport model was based on predicted sediment concentrations in the surf zone and was found to predict the rate of sediment in-filling to an acceptable level of accuracy. It is envisaged that the model will be a useful management tool, especially since it is possible to manipulate river discharges to the mouth.     

Lifespan mercury accumulation pattern in Liza aurata: Evidence from two southern European estuaries

Mercury accumulation throughout the lifespan of Liza aurata (Risso, 1810) was analysed in four tissues (muscle, gills, liver and brain) in two southern European coastal ecosystems with distinct mercury contamination. Specimens from four to five age classes were captured in two sampling sites in the Ria de Aveiro (Laranjo bay and Mira), a system historically contaminated by industrial mercury, and in one site in the Mondego estuary, assumed as a mercury-free ecosystem. Mercury concentration in all tissues was found to be significantly higher in the Ria de Aveiro (Laranjo bay) compared to the Mondego, in accordance with the environmental contamination (water, sediments and suspended particulate matter). Significant differences inside the Ria de Aveiro (between the Mira and Laranjo bay) were only detected in the liver. This tissue registered the highest levels of mercury (ranging from 0.11 to 4.2 μg g⁻¹) in all sampling sites, followed by muscle, brain, and gills. In all sampling sites and tissues was denoted a mercury dilution pattern along the lifecycle (except in liver at the Mondego, the reference area where the concentrations are always very low). An exponential trend was found in the metal age variation patterns in Laranjo (the most contaminated area) and a linear trend in the Mira and the Mondego (the least contaminated areas). Organic mercury concentration in muscle generally accounted for over 95% of total mercury concentration, and followed the same accumulation pattern of total mercury. This fish species is of lesser importance in mercury transfer to adjacent coastal areas and although the consumption of fish from Laranjo may present some risk for the humans, this risk decreases with fish age/size.     

Mercury fluxes between an impacted coastal lagoon and the Atlantic Ocean

The objective was to estimate the seasonal and inter-tidal variability of dissolved and particulate mercury fluxes between the Ria de Aveiro (Portugal) and the Atlantic Ocean. The mercury fluxes were estimated by means of a two-dimensional vertically integrated hydrodynamic model. Results showed that the particulate fraction plays an important role in the transport of mercury while the contribution of the seston fraction to the transport of mercury was always <0.5%. During spring tides, in summer, about 2% of mercury transported in seston was present in an organic form. The mass balance for the mercury fractions revealed that the mercury export to the Atlantic Ocean varied with season and tidal regime, mainly in terms of the relative importance of the dissolved and particulate fractions. An approximate range of values for the annual mass balance between 42 and 77 kg shows that the export of dissolved and particulate mercury makes little impact on the near shore region of the Atlantic Ocean and that the recovery of the lagoon from mercury contamination is likely to remain a long-term issue.     

渤海湾海河口区耗氧有机物的分布特征

渤海湾海河口区是北京、天津二大城市工业及生活污水排放入海处，是一比较典型的海域。1972年以来曾对渤海湾进行过综合性的环境污染调查和研究，但由于受调查范围和项目的限制，对河口区特别是大沽口、北塘口区有机污染物的迁移转化研究甚少，尚不足以就有机污染对河口生态环境的潜在影响作出科学判断。目前，有机污染已成为海河口区特别是其附近大城市的主要污染问题之一。本文以化学耗氧量(COD)、生物耗氧量(BOD5)、溶解氧(DO)等项目作为耗氧有机物污染程度评价的主要指标(还有氮、磷、本集另有专文讨论)，对海河口区有机污染物的迁移、转化及生态效应进行了调查研究，为有机污染评价提供数据并作初步探讨。     

基于改进的RCA水质模型对珠江口夏季缺氧及初级生产力的数值模拟研究

针对珠江口藻类生长受泥沙遮光限制明显的问题, 对RCA(row and column of Aesop)三维水质模型进行改进, 加入泥沙模块及悬沙遮光对藻类生长的限制作用。应用改进的RCA水质模型, 对珠江口的营养盐、浮游植物及溶解氧进行模拟研究, 结果显示, 改进的RCA水质模型较好地再现了洪季珠江口营养盐、浮游植物和溶解氧在水平及垂向上的空间分布, 这表明该水质模型能较好地反映珠江河口中生态因子的关键过程。珠江口的缺氧现象在物理和生化过程的共同作用下, 被限制在伶仃洋的西滩和中滩及磨刀门海域。在洪季, 大量冲淡水进入珠江口形成锋面, 颗粒态有机物(particulate organic matter, POM)在锋面的影响下, 大量集中沉降在伶仃洋的西滩及中滩特定区域及磨刀门外, 产生较高的底泥耗氧率(sediment oxygen demand, SOD)。而在高SOD的区域, 水体分层通常也较明显, 因而产生缺氧现象。另一方面, 伶仃洋水体中磷的限制作用明显, 加上悬浮泥沙的遮光作用, 不利于浮游植物生长, 使得初级生产力低; 而在陆架上, 悬沙浓度减少使初级生产力增加, 但由于海源颗粒有机碳(particulate organic carbon, POC)的沉积分散于整个陆架上, 无法产生伶仃洋内的高SOD区域, 加上水体分层不明显, 并没有产生缺氧现象。     

Transport of chemical components in sea ice and under-ice water during melting in the seasonally ice-covered Saroma-ko Lagoon,Hokkaido, Japan

Physico-chemical properties in the brine and under-ice water were measured in Saroma-ko Lagoon on the northeastern coast of Hokkaido, Japan, which is connected to the Sea of Okhotsk, during the period from mid-February through mid-March 2006. The brine within brine channels of the sea ice was collected with a new sampling method examined in this study. Salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), dissolved oxygen (DO), nutrients and oxygen isotopic ratio (δ¹⁸O) contained in the brine within brine channels of the sea ice and in the under-ice water varied largely in both time and space during the ice melt period, when discharge from Saromabetsu River located on the southeast of the lagoon increased markedly due to the onset of snow melting. The under-ice plume expands as far as 4.5 km from the river mouth at mid-March 2006, transporting chemical components supplied from the river into the lagoon. The under-ice river water was likely transported into the sea ice through well-developed brine channels in the sea ice due to upward flushing of water through brine channels occurred by loading of snowfalls deposited over the sea ice. These results suggest that the river water plume plays an important role in supplying chemical components into the sea ice, which may be a key process influencing the biogeochemical cycle in the seasonally ice-covered Saroma-ko Lagoon.     

Three main stressors acting on the Ria Formosa lagoonal system (Southern Portugal): Physical stress, organic matter pollution and the land–ocean gradient

During the last 15 years of the 20th century, several researchers carried out extensive sampling of benthic macrofauna communities in the Ria Formosa lagoon. The main objective of this paper is to discern the main communities of benthic fauna of the Ria Formosa and the leading stressors that limit them based on this large data set.The high species richness and high diversity values observed at most of the stations or groups of stations indicate a good ecological status, with the exception of the sewage-impacted areas and the physically stressed areas. It was possible to define three main stressors acting on the Ria Formosa. The most important is the physical stress imposed by the limited water renewal in some areas of the Ria Formosa. The second is the nutrient and organic matter pollution that is limited to the vicinity of the sewage outfall stations and to some locations of the Ria Formosa. This is due to the dual effects of the low residence time of water, but also due to a degradation of water quality in places of relatively restricted water circulation but with high primary production, symptoms of eutrophication. The third stressor is the natural land–ocean gradient, denoting the influence of seawater exchanges and emersion time, attenuated by the high water exchange rates of Ria Formosa.It was possible to differentiate the anthropogenic stress from the natural physical stress through the application of multivariate analysis. However, both structural (species richness and diversity indices) and functional indicators (trophic composition) indicate the same trend – low species richness, low diversity indices, and a community dominated by detritivores species at the locations characterized by high anthropogenic impact or by physical stress. The physically stressed areas were dominated by chironomid larvae and hydrobiid gastropods and the most polluted areas were dominated by oligochaetes, mainly tubificids.     

基于GAM模型对辽河公园水质的研究

基于GAM模型对2006～2011年辽河公园水质监测数据进行分析,旨在对大辽河水质进行评价。结果显示,每年pH值趋于一致;2011年溶解氧明显高于其它年份,且2006年溶解氧达到最低值。就6年的监测数据进行风险评估发现,2007年COD浓度较高且高于平均值;然而,溶解氧和COD与氨态氮的变化只有40％的相关。     

Aeromonas veronii, a tributyltin (TBT)-degrading bacterium isolated from an estuarine environment, Ria de Aveiro in Portugal

Organotin compounds are used in a variety of industrial processes therefore their subsequent discharge into the environment is widespread. Bacteria play an important role in biogeochemical transformations acting as natural decontamination agents. Therefore, screening for tributyltin (TBT)-resistant and -degrading bacteria is relevant for the selection of isolates with decontamination ability of these polluted areas. With this purpose, 50 strains were isolated from sediment and water from Ria de Aveiro and their tolerance to TBT, up to 3mM, was evaluated. Generally, occurrence of highly TBT-resistant bacteria was observed, and Gram negative bacteria exhibited more tolerance to TBT than Gram positive bacteria. A memory response was observed when bacteria were progressively exposed to increasingly higher TBT concentrations. One isolate, Aeromonas veronii Av27, highly resistant to TBT (3mM) uses this compound as carbon source and degrades it to less toxic compounds.     

A three-dimensional water quality model and its application to Jiaozhou Bay, China

A three-dimensional coupled physical and water quality model was developed and applied to the Jiaozhou Bay to study water quality involving nutrients, biochemical oxygen demand, dissolved oxygen, and phytoplankton that are closely related to eutrophication process. The physical model is a modified ECOM-si version with inclusion of flooding/draining processes over the intertidal zone. The water quality model is based on WASP5 which quantifies processes governing internal nutrients cycling, dissolved oxygen balance and phytoplankton growth. The model was used to simulate the spatial distribution and the temporal variation of water quality in the Jiaozhou Bay for the period of May 2005 to May 2006. In addition, the effect of reduction of riverine nutrients load was simulated and evaluated. The simulated results show that under the influence of nutrients discharged from river, the concentrations of nutrients and phytoplankton were higher in the northwest and northeast of the bay, and decreased from the inner bay to the outer. Affected by strong tidal mixing, the concentrations of all state variables were vertically homogeneous except in the deeper regions where a small gradient was found. Obvious seasonal variation of phytoplankton biomass was found, which exhibited two peaks in March and July, respectively. The variation of riverine waste loads had remarkable impact on nutrients concentration in coastal areas, but slightly altered the distribution in the center of the bay.     

Nutrient retention in the sediments and the submerged aquatic vegetation of the coastal lagoon of the Ria de Aveiro,Portugal

A decrease in the areas covered by seagrasses within the Ria de Aveiro, Portugal, has been observed over the past five decades, resulting in a corresponding increase of the areas of uncovered sediment supporting the growth of sparse macroalgae populations only. Presently, several macroalgae (Ulva spp., Gracilaria sp.) and one seagrass species (Nanozostera noltii (Hornem.) Toml. & Posl.) comprise the submerged aquatic vegetation (SAV) adapted to this shallow, high-energy environment, characterised by fast tidal currents and turbid waters and in which large areas of the bed are exposed during low tide. This study shows that there is a strong inter-relation between the SAV and the surface sediment in intertidal areas. The sediment covered by N. noltii was finer (median grain size 95 µm) and had a high percentage of organic matter (mean value 7.6%), compared with the sediment colonised by macroalgae (median grain size 239 µm; mean organic content 3.2%). The concentrations of both total nitrogen and phosphorous were significantly greater (P < 0.001) in surface sediments covered by N. noltii. Thus, sediments within N. noltii appear to act as a large reservoir of N and P by accumulating greater concentrations of fine sediment particles (silt and clay) and organic matter when compared with the coarser sediment covered with macroalgae only. Hence, the reduction in the area covered by seagrasses will likely result in a gradual loss of nutrients and fine sediment from the Ria de Aveiro channels.     

Plankton pulses in a temperate coastal embayment during the Winter-Spring transition

Hydrographical parameters, phytoplankton productivity and plankton composition were determined over a five-month period in the Bay of Plencia, a coastal area located in the mouth of the river Butron in Biscay, Basque Country. The water column was moderately mixed during most of the study period, which lasted from February to June 1985. Nutrient levels showed high temporal variability and were affected by both river runoff and seasonal biological processes. Nutrients were present most of the time in relatively high concentrations and most of them decreased in late spring. Phytoplankton size structure analysis showed that nanoplankton had the higher chlorophyll content and was responsible for most of the primary production. The phytoplankton showed changes in community composition resulting from the normal progression of the winter-spring conditions. Short-lived peaks of diatom concentration in the spring were followed by periods of low abundance, when maxima of Cladocera and Appendicularia occurred. Total zooplankton showed two peaks of abundance in mid-winter and mid-spring, respectively. Nauplii of Copepoda, juvenile stages of Calanoida and nauplii of Cirripedia were responsible for the two peaks, together with highly seasonal groups (Cladocera, Appendicularia and Cnidaria) in the spring maxima.Primary production seems to be driven by physical processes (temperature, short photoperiod and storms) in winter, whereas depletion of nutrients and grazing by zooplankton are responsible for phytoplankton minima between peaks of abundance in the growing season. Two temporal phases were apparent when the data were analysed by a principal component analysis.     

2015年夏季海南岛东部沿岸物理结构及浮游植物群落

琼东上升流（EHU）是南海北部最强劲的上升流系统之一。它的水动力过程已经被很多研究所揭示,但是它的浮游植物群落依然不清楚。通过利用卫星遥感数据和2015年上升流季节的航次数据,我们首次阐明了琼东上升流区域（EHU）和其临近区域雷州半岛东部上升流区（ELPU）浮游植物生物量和群落的空间结构。在夏季季风的驱动下,我们在琼东沿岸发现了一个显著的低温高盐冷舌。由于雷州半岛东部大陆架宽广平缓,ELPU比EHU相对较弱。在EHU,由于受潮汐和风浪混合的影响,高溶解氧浓度 (>6.0 mg/l)几乎从表层延伸到30米深度。其次,低溶解氧的海水(<6.0 mg/l, 缺氧)被上升流从底层抽吸到上层。ELPU和EHU相比有更差的DO状况,在EHU,底层DO浓度由于大量的消耗,浓度甚至低于3.5 mg/l。在EHU,浮游植物生物量最大值出现在30米水层而不是在表层,约为1.5 mg/m³。这表明了上升流对于浮游植物生长和DO分布的影响范围。由于营养物质输入丰富, ELPU处的浮游植物生物量比EHU高很多。在EHU处,浮游植物生物量最大值可以达到4.0 mg/m³。浮游植物生物量在EHU和ELPU的沿岸区域则降低到了大约0.2~0.3 mg/m³,而这个值与远海接近。在EHU的近岸,浮游植物群落结构被硅藻所主宰,大约占了浮游植物生物量的50%。原核生物（大约40%）、绿藻（大约20%）、原绿球藻（大约20%）组成了EHU的近岸的主要群落。在ELPU,硅藻大约占了浮游植物生物量的80%,其次是绿藻,这表明与EHU相比,这个区域是一个相对不同的生态系统。