Comparison of Estuarine Salinity Gradients and Associated Nekton Community Change in the Lower St. Johns River Estuary

Guenther, Cameron B.; MacDonald, Timothy C.

doi:10.1007/s12237-012-9544-5

Cited by 12 publications

(6 citation statements)

References 18 publications

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“…Furthermore, during the dry period, the ichthyofaunal composition was not related to the positions of sites; whereas during the wet climatic period there were clear upstream gradients in fish composition, driven mainly by freshwater species at upstream sites and marine and euryhaline taxa at downstream sites. Similar results were obtained from the lower St Johns Estuary (FL, U.S.A.) where slow ecological changes in the fish assemblage were recorded along most of the estuary salinity gradient, but rapid change was recorded at the interface between the fresh and marine waters (Guenther & MacDonald, 2012).…”

Section: Salinitysupporting

confidence: 84%

Why are there so few freshwater fish species in most estuaries?

Whitfield

2015

Journal of Fish Biology

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The freshwater fish assemblage in most estuaries is not as species rich as the marine assemblage in the same systems. Coupled with this differential richness is an apparent inability by most freshwater fish species to penetrate estuarine zones that are mesohaline (salinity: 5·0-17·9), polyhaline (salinity: 18·0-29·9) or euhaline (salinity: 30·0-39·9). The reason why mesohaline waters are avoided by most freshwater fishes is difficult to explain from a physiological perspective as many of these species would be isosmotic within this salinity range. Perhaps, a key to the poor penetration of estuarine waters by freshwater taxa is an inability to develop chloride cells in gill filament epithelia, as well as a lack of other osmoregulatory adaptations present in euryhaline fishes. Only a few freshwater fish species, especially some of those belonging to the family Cichlidae, have become fully euryhaline and have successfully occupied a wide range of estuaries, sometimes even dominating in hyperhaline systems (salinity 40+). Indeed, this review found that there are few fish species that can be termed holohaline (i.e. capable of occupying waters with a salinity range of 0-100+) and, of these taxa, there is a disproportionally high number of freshwater species (e.g. Cyprinodon variegatus, Oreochromis mossambicus and Sarotherodon melanotheron). Factors such as increased competition for food and higher predation rates by piscivorous fishes and birds may also play an important role in the low species richness and abundance of freshwater taxa in estuaries. Added to this is the relatively low species richness of freshwater fishes in river catchments when compared with the normally higher diversity of marine fish species for potential estuarine colonization from the adjacent coastal waters. The almost complete absence of freshwater fish larvae from the estuarine ichthyoplankton further reinforces the poor representation of this guild within these systems. An explanation as to why more freshwater fish species have not become euryhaline and occupied a wide range of estuaries similar to their marine counterparts is probably due to a combination of the above described factors, with physiological restrictions pertaining to limited salinity tolerances probably playing the most important role.

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Section: Salinitysupporting

confidence: 84%

Why are there so few freshwater fish species in most estuaries?

Whitfield

2015

Journal of Fish Biology

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“…Meanwhile, the isopycnal gradient at flood looks more tenuous. This is due to the strong tidal forces that bring water with a high salinity character from the sea to the mid-river area (Guenther & MacDonald, 2012).…”

Section: Vertical Characteristic Of Water Massmentioning

confidence: 99%

Distribution of Salinity and Temperature in Musi Estuary: Using Vertical Salinity Gradient for Estuary Classification Zone

Heltria

Yuliardi²,

Kismawardhani³

et al. 2022

J. Ilmu dan Teknologi Kelautan Tropis

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Musi estuary is the mouth of the Telang and Musi rivers directly adjacent to the Bangka Strait. During flood (ebb) we see the distribution of salinity increases (decreases) which is known through the vertical distribution using CTD. The TS diagram is used to see the water mass characteristics the study area. Data-Interpolating Variational Analysis (DIVA) method is used to interpolate and visualize data from vertical and spatial temperature, salinity and density data. The classification of the Musi estuary zone is identified based on the value of the distribution of salinity, which considers the exchange of circulating salinity at flood and ebb. The density of the water mass is significantly affected by the proven graded salinity. While the temperature distribution does not change significantly with depth, the spatial distribution indicates that the temperature in the estuary is lower than in the upstream and ocean areas. The spatial distribution of salinity indicates that high salinity enters the estuary towards the river further at flood than at ebb. Salinity distribution ranges from 0.5 to 30 psu and temperatures between 29 and 33 oC from horizontal and vertical sections. The pattern of salinity distribution in the Musi river estuary was identified, consisting of three zones representing salinity conditions in the study area, namely the Polyhaline, Mesohaline, and Olygohaline zones.

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“…Given the physical variability of estuarine ecosystems (e.g., [6,13,15]), consideration of the variability in the salinity field seems particularly relevant when evaluating hydrodynamic forcing on estuarine communities. This study is the first qualitative analysis of the community matrix evaluating the role of freshwater flows on aquatic communities, and the first qualitative modeling study in transitional waters based on a hydrological model [75].…”

Section: Community Models and Prediction Metricsmentioning

confidence: 99%

“…The complexity of estuarine ecosystems is influenced by the broad range and extent of anthropogenic effects in these transitional waters [1,2], including morphological and hydrological alteration [3,4], entrainment of plankton and nekton to water pumps [5,6], contaminants [3,7], introduced species [8,9], and climate change [10,11]. Changes in freshwater flow, natural or otherwise, can perturb the estuarine salinity gradient [12,13], and influence the abundance and distribution of estuarine organisms through a variety of flow-mediated processes (e.g., [9,14,15]). Moreover, estuarine food webs can be sensitive to small variations in the freshwater input [16,17].…”

Section: Introductionmentioning

confidence: 99%

Modeling the Influence of Outflow and Community Structure on an Endangered Fish Population in the Upper San Francisco Estuary

Castillo

2019

Water

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The aim of this community modeling study was to evaluate potential mechanisms by which freshwater outflow in the upper San Francisco Estuary, CA, controls the fall habitat and abundance of subadult delta smelt Hypomesus transpacificus and its community. Through analyses of the community matrix, community stability and the direction of change of community variables were qualitatively and quantitatively modeled under four outflow–input scenarios. Three subsystems were modeled in the low salinity zone (1–6 psu), each overlapping the location corresponding to the distance from the mouth of the estuary to upstream positions where the near-bottom 2 psu isohaline (X2) is at 74, 81, and 85 km (corresponding to high-, mid-, and low-outflows). Results suggested communities were qualitatively stable at each X2 position, but simulations showed the percent of stable models decreased from low- to high-X2 positions. Under all outflow–input scenarios, the predicted qualitative population responses of delta smelt were: (1) consistently positive for the low X2 position, and (2) uncertain under both mid- and high-X2 positions. Qualitative predictions were generally consistent with quantitative simulations and with the relations between relative abundance of delta smelt and X2. Thus, high outflow seems beneficial to subadult delta smelt when X2 reaches 74 km during fall.

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Comparison of Estuarine Salinity Gradients and Associated Nekton Community Change in the Lower St. Johns River Estuary

Cited by 12 publications

References 18 publications

Why are there so few freshwater fish species in most estuaries?

Why are there so few freshwater fish species in most estuaries?

Distribution of Salinity and Temperature in Musi Estuary: Using Vertical Salinity Gradient for Estuary Classification Zone

Modeling the Influence of Outflow and Community Structure on an Endangered Fish Population in the Upper San Francisco Estuary

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