Factors Influencing Colonization and Survival of Juvenile Blue Crabs Callinectes sapidus in Southeastern U.S. Tidal Creeks

Tidal creeks along the southeastern U.S. and Gulf of Mexico coastlines provide nursery habitats for commercially and ecologically important nekton, including juvenile blue crabs Callinectes sapidus, a valuable and heavily landed seafood species. Instream and watershed urbanization may influence the habitat value that tidal creeks provide to blue crabs. We investigated natural and anthropogenic factors influencing juvenile blue crab occupancy dynamics in eight first-order tidal creeks in coastal North Carolina (USA). An auto-logistic hierarchical multi-season (dynamic) occupancy model with separate ecological and observation sub-models was fitted to juvenile blue crab presence/absence data collected over replicate sampling visits in multiple seasons at three fixed trapping sites in each creek. Colonization and survival are the processes operating on occupancy that are estimated with this formulation of the model. Covariates considered in the ecological sub-model included watershed imperviousness, the percent of salt marsh in each creek’s high tide area, percent salt marsh edge, site-level water depth, and site-level salinity. Temperature, salinity, and dissolved oxygen were covariates considered in the observation sub-model. In the ecological sub-model, watershed imperviousness was a meaningful negative covariate and site-level salinity was a positive covariate of survival probability. Imperviousness and salinity were each marginally meaningful on colonization probability. Water temperature was a positive covariate of detection probability in the observation sub-model. Mean estimated detection probability across all sites and seasons of the study was 0.186. The results suggest that development in tidal creek watersheds will impact occupancy dynamics of juvenile blue crabs. This places an emphasis on minimizing losses of natural land cover classes in tidal creek watersheds to reduce the negative impacts to populations of this important species. Future research should explore the relationship between imperviousness and salinity fluctuations in tidal creeks to better understand how changing land cover influences water chemistry and ultimately the demographics of juvenile blue crabs.

Developing a Water Quality Assessment Framework for Southwest Florida Tidal Creeks

The three contiguous National Estuary Programs of southwest Florida, along with partners from six coastal counties, have developed a tidal creek water quality assessment framework to help prioritize natural resource investigations across a large population of tidal creeks between Tampa Bay and Estero Bay, Florida. The assessment framework is based on outcomes of a multidisciplinary study and includes a nutrient based report card that characterizes nutrient conditions relative to regional numeric nutrient criteria developed for contributing freshwater streams, identification of site-specific water quality indicators of tidal creek condition, and an online open science dashboard to display the assessment framework and provide access to all information relevant to its implementation. Application of the assessment framework has provided an actionable list of southwest Florida tidal creeks prioritized for further research and potential management action along with a host of site-specific indicator results that provide insights into drivers of tidal creek condition. The open science dashboard provides a platform for dissemination of this information in a readily accessible and reproducible format and a means to incorporate new data and indicators as they become available. Local resource managers are in need of tools to help prioritize natural resource investigations and management actions that achieve the greatest resource benefit with limited available resources. This assessment framework informs these efforts and builds capacity for future research to identify and refine management tools for these creeks where management resources, data, and sentinel biological response endpoints are limited.

Variability in the zooplankton assemblages in relation to environmental variables in the tidal creeks of Sundarban estuarine system, India

The present study illustrates a holistic account of zooplankton community dynamics in relation to physico − chemical variables in the tidal creeks of Indian Sundarbans estuarine system. Out of 11 water parameters, seven parameters (Temp., salinity, DO, turbidity, PO4 − P, NO3 − N and NO2 − N) differed significantly (p ≤ 0.05) among seasons. A total of 63 zooplankton taxa were recorded with the predominance of Copepoda, varying in ranges from 59.55 to 73.13% of the total zooplankton population. PERMANOVA design depicted the significant variations of zooplankton population both spatially (F = 2.313; p = 0.001) and temporally (F = 6.107; p = 0.001). Out of 41 species of Copepoda recorded, 14 species (Paracalanous parvus, Parvocalanous dubia, Bestiolina similis, Acrocalanous gibber, A. gracilis, Acartia erythraea, A. spinicauda, Pseudodiaptomus serricaudatus, P. annandalei, P. aurivilli, Oithona brevicornis, O. similis, Longipedia weberi and Microsetella norvegica) indicated as ‘characterizing species’ in the creek environment, and highlighted the euryhaline nature as well as broad range of thermal tolerance of these species. β – diversity index (Index of Multivariate dispersion) reflected higher values (β = >1) in the creeks (S4, S2 and S6), those are experienced with high anthropogenic pressure. On the whole, the calculated mean value of α − diversity (dʹ=4.07; H'=2.31) indicated ‘good’ zooplankton diversity. Water parameters viz., Temp., salinity, DO, turbidity, PO4 − P and NO3 − N were found to have influence on the distribution, abundance and diversity of zooplankton in the creeks. More specifically, the linear model (DistLM) exhibited two variables viz., temperature and salinity were the primary controlling factors in shaping the zooplankton community compositions in the creek environment.

Variations of surface water quality in selected tidal creeks of Sagar Island, Indian Sundarban eco-region: a multivariate approach

Sagar Island in Indian Sundarbans is bestowed with numerous tidal creeks providing a suitable home to its inherent aquatic biota. The present study investigated the variation in the surface water quality in selected tidal creeks of Sagar Island, Indian Sundarbans to understand the present status of water quality for wildlife propagation and fisheries. Ten water parameters were taken into consideration for analysis on monthly basis from four stations (tidal creeks) from September 2015 to August 2016. One-way ANOVA showed five parameters (water temperature, salinity, dissolved oxygen, turbidity and chemical oxygen demand) varied significantly between seasons (p ≤ 0.05). Factor analysis exhibited four factors explaining 53.21% total variance in the observed data. Salinity and turbidity showed a maximum annual range of variations followed by dissolved oxygen. The fluctuations of physicochemical parameters throughout the year hinted toward the ever-changing nature of the estuarine ecosystem with possible human-induced impacts. Pronounced variation in turbidity seemed to be the effect of ferrying/transportation, monsoonal runoff and other human-induced activities. In the present study, water parameters viz., water temperature, dissolved oxygen and turbidity were the deterministic parameters influencing the variables in the system. The other important parameters were found to be COD, BOD3 and nitrate concentrations during the study period. The study shall provide baseline information in formulating the management measures in terms of water quality in wildlife propagation and fisheries.

Interferences of trace metals between sediment and Dotillid crab (Ilyoplax frater) from three tidal creeks, Karachi, Pakistan

In the Anthropocene era, an immersion of toxic substances, i.e., trace metals, has been enhanced in the marine environment not only due to urban sprawl and industrial development but predominantly owing to incongruous management and lack of sustainable approaches. The coastal region of Pakistan shares a similar obstacle as most of the developing countries confronted. Therefore, this study was designed to investigate concentrations of eight metals (Cu, Fe, Zn, Ni, Co, Pb, Cr, and Cd) in sediment and Dotillid crab, Ilyoplax frater, at three tidal creeks in Karachi, Pakistan. All metals in sediments and crabs were analyzed by atomic absorption spectrometer. The sediment pollution was evaluated by contamination degree (CD) and potential ecological risk index (RI). After depicting the metal pollution in sediments, metal accumulation, and contamination in benthic crab were investigated through total metal concentrations in crabs, accumulation factor (AF), correlation analysis, and regression analysis. The results exhibited substantial differences in the concentrations of Zn, Ni, Pb, Cr, and Cd among the tidal creek sediments. Contamination factors indicated that the Cd and Pb had the highest sharing in sediment pollution, and the tidal creeks classified as moderately contaminated. All metal accumulations in Dotillid crabs showed notable spatial variations, and accumulation factors (AFs) for most of the metals were > 1.0, signifying the strong bioaccumulation of metals in crabs. Particularly, Cu, Co, and Cd levels were considerably greater (two to three times) in Dotillid crabs compared to creek’s sediments, even though they don’t share any relationship between two matrixes. Hydrographical and sedimentological traits also revealed significant interactions with metal levels in sediments and crabs. A substantial association was also noticed in Fe, Ni, and Pb between sediments and crabs. Interestingly, most of the metal AFs showed a notable inverse correlation with the environmental matrix. Exceptionally, a strong positive correlation found between the Pb concentration in crabs and sediments suggested that I. frater probably acts as an indicator of Pb pollution.