Stability of Bacterial Composition and Activity in Different Salinity Waters in the Dynamic Patos Lagoon Estuary: Evidence from a Lagrangian-Like Approach

We employed a Lagrangian-like sampling design to evaluate bacterial community composition (BCC—using temporal temperature gel gradient electrophoresis), community-level physiological profiles (CLPP—using the EcoPlate? assay), and influencing factors in different salinity waters in the highly dynamic Patos Lagoon estuary (southern Brazil) and adjacent coastal zone. Samples were collected monthly by following limnetic–oligohaline (0–1), mesohaline (14–16), and polyhaline (28–31) waters for 1 year. The BCC was specific for each salinity range, whereas the CLPPs were similar for mesohaline and polyhaline waters, and both were different from the limnetic–oligohaline samples. The limnetic–oligohaline waters displayed an oxidation capacity for almost all organic substrates tested, whereas the mesohaline and polyhaline waters presented lower numbers of oxidized substrates, suggesting that potential activities of bacteria increased from the polyhaline to oligohaline waters. However, the polyhaline samples showed a higher utilization of some simple carbohydrates, amino acids, and polymers, indicating a shortage of inorganic nutrients (especially nitrogen) and organic substrates in coastal saltwater. The hypothesis of bacterial nitrogen limitation was corroborated by the higher Nuse index (an EcoPlate?-based nitrogen limitation indicator) in the polyhaline waters and the importance of NO₂ ^?, NO₃ ^?, low-molecular-weight substances, and the low-molecular-weight:high-molecular-weight substances ratio, indicated by the canonical correspondence analyses (CCAs). Our results demonstrate the important stability of microbial community composition and potential metabolic activity in the different water salinity ranges, which are independent of the region and time of the year of sample collection in the estuary. This is a quite unexpected result for a dynamic environment such as the Patos Lagoon estuary.     

Estuarine fish communities respond to climate variability over both river and ocean basins

Estuaries are dynamic environments at the land–sea interface that are strongly affected by interannual climate variability. Ocean–atmosphere processes propagate into estuaries from the sea, and atmospheric processes over land propagate into estuaries from watersheds. We examined the effects of these two separate climate‐driven processes on pelagic and demersal fish community structure along the salinity gradient in the San Francisco Estuary, California, USA. A 33‐year data set (1980–2012) on pelagic and demersal fishes spanning the freshwater to marine regions of the estuary suggested the existence of five estuarine salinity fish guilds: limnetic (salinity = 0–1), oligohaline (salinity = 1–12), mesohaline (salinity = 6–19), polyhaline (salinity = 19–28), and euhaline (salinity = 29–32). Climatic effects propagating from the adjacent Pacific Ocean, indexed by the North Pacific Gyre Oscillation (NPGO), affected demersal and pelagic fish community structure in the euhaline and polyhaline guilds. Climatic effects propagating over land, indexed as freshwater outflow from the watershed (OUT), affected demersal and pelagic fish community structure in the oligohaline, mesohaline, polyhaline, and euhaline guilds. The effects of OUT propagated further down the estuary salinity gradient than the effects of NPGO that propagated up the estuary salinity gradient, exemplifying the role of variable freshwater outflow as an important driver of biotic communities in river‐dominated estuaries. These results illustrate how unique sources of climate variability interact to drive biotic communities and, therefore, that climate change is likely to be an important driver in shaping the future trajectory of biotic communities in estuaries and other transitional habitats.     

Radium in the Suwannee River and estuary

A two-year study of radium in the Suwannee River has shown that groundwater discharge, via springs, is a very important source of radium both to the river and to offshore Gulf of Mexico waters. Dissolved radium is maintained within relatively narrow limits in the river by uptake into suspended particles. In the estuary, dissolved radium versus salinity profiles show distinctive nonconservative behavior with radium in significant excess of its linear mixing value at mid-salinities. Unlike the situation in many other estuaries, however, desorption of radium from particles cannot account for most of the observed excess. Thus, the anomalously high radium characteristic of much of the west Florida shelf apparently does not have a riverine source. Direct effusion of high-radium groundwater into these coastal waters is thought to be the major supplier of radium, and perhaps other elements as well.     

Radium in the Suwannee River and estuary

A two-year study of radium in the Suwannee River has shown that groundwater discharge, via springs, is a very important source of radium both to the river and to offshore Gulf of Mexico waters. Dissolved radium is maintained within relatively narrow limits in the river by uptake into suspended particles. In the estuary, dissolved radium versus salinity profiles show distinctive nonconservative behavior with radium in significant excess of its linear mixing value at mid-salinities. Unlike the situation in many other estuaries, however, desorption of radium from particles cannot account for most of the observed excess. Thus, the anomalously high radium characteristic of much of the west Florida shelf apparently does not have a riverine source. Direct effusion of high-radium groundwater into these coastal waters is thought to be the major supplier of radium, and perhaps other elements as well.     

Phytoplankton assemblages across the marine to low-salinity transition zone in a blackwater dominated estuary

Along the salinity gradient between the freshwater reach ofthe Suwannee River and the marine waters of the Gulf of Mexico,the spatial and temporal composition and abundance of phytoplanktonwas examined in relation to physical and chemical water-columnvariables (i.e. salinity, nutrient and light availability andtemperature). The goal of this study was to explore the applicabilityof the concepts of ecotone and ecocline to the distributionof phytoplankton. This was undertaken in a relatively open estuarydominated by a tannin-colored river, the Suwannee River, alongthe central northwest coast of Florida, USA. Hierarchical clusteranalysis and non-metric multi-dimensional scaling (MDS) wasused to define biologically distinct regions within the estuarybased on the composition of phytoplankton. Variations in phytoplanktonassemblages in relation to environmental variables were investigatedusing a canonical correspondence analysis. The results indicatethat in addition to the alignment of phytoplankton compositionalong a salinity gradient, several key environmental factorsinfluence phytoplankton assemblages within hydrologically distinctregions of the estuary supporting an ecocline view. However,the distribution of dinoflagellate assemblages were in contrastto the more temporally fluid spatial distributions of cyanobacteriaand diatoms in the Suwannee River estuary. The spatially definednature of the dinoflagellate assemblages was more characteristicof an ecotone rather than an ecocline.     

Feeding habitats of the Gulf sturgeon, Acipenser oxyrinchus desotoi, in the Suwannee and Yellow rivers, Florida, as identified by multiple stable isotope analyses

Stable ¹³C, ¹⁵N, and ³⁴S isotopes were analyzed to define the feeding habitats of Acipenser oxyrinchus desotoi in the Suwannee and Yellow River populations. For the majority (93.9%) of Suwannee subadults and adults, ¹³C and ³⁴S signatures indicate use of nearshore marine waters as primary winter feeding habitat, probably due to the limiting size of the Suwannee Sound estuary. In the Yellow River population, ¹³C isotope signatures indicate that adults remain primarily within Pensacola Bay estuary to feed in winter, rather than emigrating to the open Gulf of Mexico. A minor Suwannee River subset (6% of samples), comprised of juveniles and subadults, displayed ¹³C signatures indicating continued feeding in freshwater during the spring immigration and fall emigration periods. This cannot be interpreted as incidental feeding since it resulted in a 20.5% turnover in tissue ??¹³C signatures over a 1?C3?month period. Cessation of feeding in the general population does not coincide with high river water temperatures. The hypothesis of reduced feeding in freshwater due to localized prey depletion as a result of spatial activity restriction is not supported by the present study. Instead, Suwannee River A. o. desotoi appear to follow two trophic alternatives; 1) complete cessation of feeding immediately upon immigration in spring, continuing through emigration 8?C9?months later (the predominant alternative); 2) continued intensive feeding for 1?C3?months following immigration, switching to freshwater prey, selected primarily from high trophic levels (i.e., large prey). Stable ??³⁴S data verifies that recently immigrated, fully-anadromous A. o. desotoi adults had fed in nearshore marine waters, not offshore waters.     

Seasonal and environmental influences on recruitment patterns and habitat usage among resident and transient fishes in a World Heritage Site subtropical estuary

This study investigated whether the fish communities inhabiting shallow non‐vegetated habitats in two divergent bays in a subtropical World Heritage Site estuarine system differed according to wet (spring–summer) and dry (autumn–winter) seasons or polyhaline and mesohaline zones, within the broader objective of facilitating spatio‐temporal management. Species richness (total of 74 taxa; total length, L_T = 11–552 mm) and abundance (51 109 individuals) were mostly greater in the wet than dry season and in polyhaline than mesohaline areas. There was a major effect of rainfall on recruitment, particularly among transient fishes, which could be the result of enhanced survival of young via greater productivity (food resources) and protection from predators (via turbidity reducing visual cues). Salinity had strong interactive effects with rainfall and temperature in one bay, with greater species richness and overall abundances as well as large abundances of four key species [Anchoa januaria and Atherinella brasiliensis (pelagic residents), Cetengraulis edentulus (pelagic transient) and Diapterus rhombeus (demersal transient)] during the wet season in polyhaline areas; possibly reflecting a biodiversity hotspot that might be affected by distance to the estuary mouth and convergence hydrology. Regionally, the results support enforcing spatio‐temporal restrictions to minimize anthropogenic activities within statutory (but not always enforced) protected areas. Globally, the data reiterate the need to identify and understand biotic and abiotic effects on estuarine ichthyofaunal distributions and abundances as a precursor to their management.     

The temporal variation of intertidal nematodes in the Westerschelde I. The importance of an estuarine gradient

Biannual meiobenthic sampling (Spring and Autumn) was carried out in 1983–1989 at two fine sandy intertidal stations in the Westerschelde estuary. Both stations are exposed daily for more than one hour and are situated in the polyhaline and the mesohaline zone of the estuary. Average density data of non-selective deposit-feeders > predators > epigrowth-feeders > selective deposit-feeders for both stations are presented in spite of different nematode species composition. No difference between Spring and Autumn nor trend over 7 years could be detected. Higher total nematode densities are found at the polyhaline station (average 3200 ind. 10 cm^?2) in comparison with the mesohaline station (average 2300 ind. 10 cm^?2), a difference mainly due to higher non-selective deposit-feeders and predators densities in the polyhaline station. Each year, heterogeneous variance is found for all feeding types at the mesohaline station, but only for epigrowth-feeders and predators at the polyhaline station. The higher nematode density at the polyhaline station is probably caused by the more stable nematode structure. An unstable nematode temporal pattern at the mesohaline station is suggested to be combined with the detritus food chain system in the mesohaline zone. The unstable estuarine habitats are mainly caused by their upstream effects: the River Schelde, which clearly influences the stability of the nematode communities.     

Seasonal distribution of juvenile Atlantic cod in the southern Gulf of St Lawrence

Seasonal changes in the geographic distribution of juvenile (ages 1–4) Atlantic cod Gadus morhua were determined from research surveys conducted in the southern Gulf of St Lawrence during 1986–87, 1990–91, and 1994. From late June to early October, juvenile cod were most abundant in shallow water (<50 m deep). By early November, all age groups (adults and juveniles) had migrated to deep (>100 m) offshore waters for the winter. For most juveniles, this represented a minimum migration of >225 km (each way). Age 3 and 4 cod migrated greater distances than age 1 and 2 fish. Some age 3 and 4 cod migrated as far as 650 km from their summer and early autumn areas. Although there was partial geographic segregation of juvenile and adult fish during summer and winter, all age groups were found together during the migration. No cod were present in the shallow waters (<80 m deep) of the south-western Gulf during April due, in part, to later than average ice-melt. Large numbers of all age-classes were present in most of the south-eastern Gulf by mid-May.     

Zonation of intertidal macrobenthos in the estuaries of Schelde and Ems

Based on data, collected in 1980–1990, the intertidal benthic macrofauna of the Schelde and Ems estuaries was compared. The spatial occurrence of the benthic macrofauna along the salinity gradient, including the freshwater tidal area was emphasized. Both estuaries appeared to have a very similar species composition, especially at genus level. The higher number of species observed in the Schelde estuary was probably due to a greater habitat diversity. In both estuaries species diversity decreased with distance upstream. The total density did not vary along the estuarine gradient, whereas biomass is highest in the polyhaline zone.In both estuaries distinct intertidal benthic communities were observed along the salinity gradient: a marine community in the polyhaline zone, a brackish community in the mesohaline zone, and a third community in the oligohaline and freshwater tidal zones of the estuary. These three communities were very similar between both estuaries. Their main characteristics were discussed together with the occurrence and distribution of the dominant species.For the Schelde estuary and to a lesser extent also for the Ems estuary, there was evidence that anthropogenic stress had a negative effect on the intertidal macrobenthic communities of the oligohaline/freshwater tidal zone. Only Oligochaeta were dominating, whereas the very euryhaline and/or true limnetic species were missing. In the mesohaline zone, the Schelde estuary was dominated by large numbers of short-living, opportunistic species, whereas in the Ems estuary relatively more stable macrobenthic communities were observed. A comparison with some other European estuaries showed in general similar trends as those observed for the Schelde and Ems estuaries.     

Nanosilver inhibits nitrification and reduces ammonia‐oxidising bacterial but not archaeal amoA gene abundance in estuarine sediments

Silver nanoparticles (AgNPs) enter estuaries via wastewater treatment effluents, where they can inhibit microorganisms, because of their antimicrobial properties. Ammonia‐oxidising bacteria (AOB) and archaea (AOA) are involved in the first step of nitrification and are important to ecosystem function, especially where effluent discharge results in high nitrogen inputs. Here, we investigated the effect of a pulse addition of AgNPs on AOB and AOA ammonia monooxygenase (amoA) gene abundances and benthic nitrification potential rates (NPR) in low‐salinity and mesohaline estuarine sediments. Whilst exposure to 0.5 mg L^?1 AgNPs had no significant effect on amoA gene abundances or NPR, 50 mg L^?1 AgNPs significantly decreased AOB amoA gene abundance (up to 76% over 14 days), and significantly decreased NPR by 20‐fold in low‐salinity sediments and by twofold in mesohaline sediments, after one day. AgNP behaviour differed between sites, whereby greater aggregation occurred in mesohaline waters (possibly due to higher salinity), which may have reduced toxicity. In conclusion, AgNPs have the potential to reduce ammonia oxidation in estuarine sediments, particularly where AgNPs accumulate over time and reach high concentrations. This could lead to long‐term risks to nitrification, especially in polyhaline estuaries where ammonia‐oxidation is largely driven by AOB.     

Assessment of the seasonal usage of the lower Pascagoula River estuary by Gulf sturgeon (Acipenser oxyrinchus desotoi)

The Pascagoula watershed likely offers the greatest possibility for the survival of the Gulf sturgeon, Acipenser oxyrinchus desotoi, within Mississippi. Thus, understanding and preserving the connectivity between distant habitats in this region plays a major role in protecting and managing such anadromous fish populations. The focus of this project was to determine the within‐river routes Gulf sturgeon take through the lower Pascagoula River downstream of the point where it splits (river kilometer 23) into two distinct distributaries. Sixty days were sampled throughout a two‐year period with a total effort of 81 947 net‐meter‐hours and eight Gulf sturgeon were captured, ranging from 74 to 189 cm FL and weighing from 3.6 to 52.6 kg. Using an array of automated telemetry receivers, acoustically tagged Gulf sturgeon movements were monitored within the lower river and associated estuary. Estimated residence times (days) suggest Gulf sturgeon appear to prefer the eastern distributary upriver from Bayou Chemise as the primary travel corridor between freshwater habitats and marine feeding grounds. The western distributary mouth was more highly used by Gulf sturgeon during both seasonal migrations between upriver and offshore habitats. Thus, the western distributary appears to represent the main entrance point utilized by Gulf sturgeon to the Pascagoula River watershed and should be protected as the eastern distributary mouth has been altered from a natural marsh edge to one of hardened surfaces.     

Restoration flows for the Colorado River estuary, México: estimates from oxygen isotopes in the bivalve mollusk Mulinia coloradoensis (Mactridae: Bivalvia)

Because of competing demands for freshwater, restoration of estuaries requires estimates of inflows to sustain key species. In this study we estimated the pre-dam salinities of the Colorado River estuary by using oxygen isotopes in subfossil shells of the bivalve mollusk Mulinia coloradoensis. Since the construction of upstream dams and water diversions, average salinity in the estuary has increased to 38 practical salinity units (psu) and the population of M. coloradoensis has decreased by ~90%. In the pre-dam estuary, specimens grew when salinity ranged from 22 to 33?psu at the mouth of the river while populations 40?km distant grew at salinities from 30 to 38?psu. The river flow needed to reduce salinities at the mouth of the river to those recorded in the most distant localities (40?km from river??s mouth) ranges from 120 to 290?m³?s^?1. If these flows were sustained for a year, they would total 7?C16?% of the river??s annual average historical flow (~1.8?×?10¹⁰?m³).     

Spatial and seasonal distribution of the tuna catch on floating objects in the eastern pacific ocean during 1992–1993

An analysis of the catch associated with floating objects by the Mexican tuna purse‐seine fleet in the eastern Pacific Ocean during 1992–1993 was made to determine the spatial and seasonal distribution. The information used was generated by observers of the Programa Nacional de Aprovechamiento del Atun y Protección a los Delfines (PNAAPD). There was no clear seasonal and spatial distribution of floating objects examined in this study, however there were areas where floating objects were more common; the mouth of the Gulf of California, waters offshore Peru, and in oceanic waters. The largest catch of yellowfin tuna was offshore of Peru in winter. Two areas with largest (length) yellowfin tuna were the mouth of the Gulf of California and offshore Peru. For skipjack tuna, the largest catch was offshore Peru in winter, but the largest skipjack were caught between 120° and 130°W along 10°N in spring. The largest yellowfin tuna were captured by sets on bamboo, fish aggregating devices (FADs), planks and boards, and logs (trees or parts). The largest skipjack were captured by sets on dead whales, kelp paddies, planks and boards, and pallets and crates. Most of the sets were made during the early hours of the day but an important number of log sets were made in the early afternoon. For the period analyzed, floating objects were more frequent during fall and winter with the area offshore of Peru the most important.     

Environmental influences on the spatial ecology of juvenile smalltooth sawfish (Pristis pectinata): results from acoustic monitoring

To aid recovery efforts of smalltooth sawfish (Pristis pectinata) populations in U.S. waters a research project was developed to assess how changes in environmental conditions within estuarine areas affected the presence, movements, and activity space of this endangered species. Forty juvenile P. pectinata were fitted with acoustic tags and monitored within the lower 27 km of the Caloosahatchee River estuary, Florida, between 2005 and 2007. Sawfish were monitored within the study site from 1 to 473 days, and the number of consecutive days present ranged from 1 to 125. Residency index values for individuals varied considerably, with annual means highest in 2005 (0.95) and lowest in 2007 (0.73) when several P. pectinata moved upriver beyond detection range during drier conditions. Mean daily activity space was 1.42 km of river distance. The distance between 30-minute centers of activity was typically <0.1 km, suggesting limited movement over short time scales. Salinity electivity analysis demonstrated an affinity for salinities between 18 and at least 24 psu, suggesting movements are likely made in part, to remain within this range. Thus, freshwater flow from Lake Okeechobee (and its effect on salinity) affects the location of individuals within the estuary, although it remains unclear whether or not these movements are threatening recovery.     

长江口冬季和春季浮游植物的粒级生物量

根据2005年2月28日—3月10日和5月30日—6月4日在长江口及其邻近水域进行的多学科综合外业调查,报道了冬季和春季浮游植物粒级生物量的空间分布和组成特征,并探讨了影响浮游植物粒级生物量的环境因子.结果表明：冬季长江口及其邻近水域表层叶绿素a平均浓度为1.28 mg·m^-3,高值区集中在口门附近;小粒径浮游植物（<20 μm）对浮游植物生物量的贡献率为66.7%,但在冲淡水区大粒径浮游植物（>20 μm）占据优势.春季长江口及其邻近水域表层叶绿素a浓度大幅增加,口门内、外的平均值分别为0.67和6.03 mg·m^-3,122.5°—123.0° E间水域因水华爆发出现显著的叶绿素a高值区;小粒径浮游植物对浮游植物生物量的贡献高达83.5%,其优势在水华区尤为明显.典型站位浮游植物粒级生物量的垂向分布显示,2种粒径浮游植物叶绿素a浓度的差异随水深增加而减小,至底层二者浓度相当.根据所获的环境因子资料,盐度和营养盐是影响长江口及其邻近水域浮游植物粒级生物量分布和组成的重要环境因子.     

Evidence of autumn spawning in Suwannee River Gulf sturgeon,Acipenser oxyrinchus desotoi (Vladykov, 1955)

Evidence of autumn spawning of Gulf sturgeon Acipenser oxyrinchus desotoi in the Suwannee River, Florida, was compiled from multiple investigations between 1986 and 2008. Gulf sturgeon are known from egg collections to spawn in the springtime months following immigration into rivers. Evidence of autumn spawning includes multiple captures of sturgeon in September through early November that were ripe (late‐development ova; motile sperm) or exhibited just‐spawned characteristics, telemetry of fish that made >175 river kilometer upstream excursions to the spawning grounds in September–October, and the capture of a 9.3 cm TL age‐0 Gulf sturgeon on 29 November 2000 (which would have been spawned in late September 2000). Analysis of age‐at‐length data indicates that ca. 20% of the Suwannee River Gulf sturgeon population may be attributable to autumn spawning. However, with the very low sampling effort expended, eggs or early life stages have not yet been captured in the autumn, which would be the conclusive proof of autumn spawning. More sampling, and sampling at previously unknown sites frequented by acoustic telemetry fish, would be required to find eggs.     

An ecological study of the Ponggol Estuary in Singapore

1. An ecological study of the Ponggol Estuary was conducted from July 1965 to June 1966 and the seasonal data on physical, chemical and biological characteristics were presented.
2. The Ponggol River represents a short, narrow and shallow estuary in Singapore. The river mouth is open throughout the year and water from eastern Johore Straits drains in twice a day at high tide. The upper reach, however, is left exposed at low tide.
3. The Ponggol River was classified as a vertically and laterally homogeneous estuary and was found to exhibit a mesohaline to polyhaline environment.
4. Significant hydrological gradients from the river mouth 10 the upper reach were noted in the river system. Salinity, dissolved oxygen and pH increased towards the mouth of the river and other parameters such as nutrients, dissolved organic matter and turbidity increased towards the source.
5. Although the river received organic pollutants at the upper reach the estuary was able to discharge them fairly rapidly through regular flushing by the tides. The transient rise of organic matter did not appear to impart any serious affect on the biota in the estuary.
6. Over 98% of the phytoplankton consisted of diatoms, most of which were brought into the estuary from eastern Johore Straits. Freshwater forms were relatively few.
7. Phytoplankton biomass was considerably higher than the adjoining waters. and was reduced at the upper reach due to high turbidity of the water.
8. 80% of the zooplankton was composed of dinoflagellates,Difflugia, copepods and bivalve larvae dominating at all sections of the estuary.
9. Percentage composition of the zooplankton showed that dinoflagellates and copepod nauplii predominated at high tide whileDifflugia and bivalve larvae were abundant at low tide.
10. Zooplankton standing crop, in general, was higher towards the source at high tide but the reverse was found at low tide, i.e. standing crop increased towards the river mouth. This was attributed to the process of concentration.
11. Species composition of zooplankton was found to be more or less similar to that of the eastern Johore Straits.
12. The nekton consisted predominantly of small and juvenile fish. Close correlation of fish and copepods was found to be statistically valid and it was concluded that the fish entered the estuary to feed rather than to spawn.
13. The squids formed an important catch of the beach seine unit and were caught throughout the year.
14. The fish population could be grouped into four categories: estuarine components, euryhaline components, marine components and migratory components.
15. Benthic invertebrates were abundant. Commercially important species consisted of prawns,Metapenaeus andPenaeus, and crabs,Neptunus pelagicus andScylla serrata.
16. The river bed was inhabited predominantly by molluscs and the distribution resembled that of the sheltered shore of muddy-sand type.

     

春夏季闽江口和兴化湾虾类数量特征

本文利用2008年4月和9月闽江口和兴化湾海域渔业资源调查资料,研究这两个不同类型海域虾类密度的时空分布,优势种特征、地形地貌、海流和水文等因素对分布的影响。结果表明,4月闽江口虾类生物量(22.05kg/km₂)低于兴化湾生物量(23.33kg/km₂), 而尾数密度(12.34?10₃ ind./ km₂)高于兴化湾尾数密度(8.42?103 ind./ km₂),9月也是如此,闽江口虾类生物量(205.54kg/km₂)低于同期兴化湾生物量(329.60kg/km₂),但尾数密度(131.25?10₃ ind./ km₂)大于兴化湾尾数密度(95.79?10₃ ind./ km₂)。这一现象的产生,与闽江口和兴化湾虾类资源种类规格特征有一定的关系：依据优势性分析,在兴化湾,优势种以广盐性大规格的哈氏仿对虾为主,其它主要优势种优势性不明显,对总生物量变化的贡献不大。反观闽江口的优势种,除了广盐性的哈氏仿对虾,还有个体数量巨大的半咸水小规格中国毛虾,其中,中国毛虾尾数密度的百分比占了虾类的大部分。不同盐度环境,种类对不同盐度环境盐度适应是形成闽江口和兴化湾优势种不同格局的主要原因。在闽江口,南部渔场是当地的主要渔场,9月是主要的渔汛,与闽江径流量的季节变化和闽江口地形地貌特征有关。在兴化湾,湾口是虾类的主要产卵场和索饵场,湾外则是虾类越冬场,与构成资源主要种类哈氏仿对虾暖水性和兴化湾水团特征有关。不同季节比较,在9月,兴化湾和闽江口虾类资源品种呈现多样化的趋势,兴化湾和闽江口比较,闽江口虾类资源品种呈现更加多样化的特征。