The Laurentian Great Lakes represent the largest freshwater basin on Earth, containing 21% of the world's surface fresh water by volume. Water level fluctuations are an on-going concern and have received considerable attention in the area. We present a trend analysis of meteorological (air temperature, cloud cover, and wind speed) and hydrological (precipitation, runoff, and evaporation) variables for Lake Michigan, Lake Huron, and Georgian Bay. Using the non-parametric Mann-Kendall test, our analysis identified significant upward trends in daily minimum air temperature, whereas daily maximum air temperature demonstrated weakly decreasing trends in space and time. Evaporation was found to be increasing from late spring until early fall and this pattern may be explained by the shortening of the ice/snow cover period, which results in faster warming of lake surface due to the induced variations in albedo feedback. Time-series analysis of the over-lake precipitation revealed mostly non-significant statistical trends. Recent temperature increases may have led to elevated winter runoff in the Great Lakes region, given that precipitation falls mainly as rain instead of snow. We also provide clear evidence of reduced cloud cover and wind speed. Our study offers critical insights into the patterns of within- and among-year variability of hydro-meteorological variables useful in elucidating the mechanisms that modulate water levels in the Great Lakes.

We developed and validated a Planktonic Index of Biotic Integrity for subtropical reservoirs to assess their ecosystem health. For this purpose, we analyzed the phytoplankton and zooplankton communities and determined reservoir trophic status in the Paranapanema River system (Southeast Brazil). Eleven dams were constructed in the main course of this river to supply hydropower plants. Three of the reservoirs are accumulation systems (i.e. with high water retention times), whereas the others are run-of-the-river systems. For the study the three larger reservoirs (Jurumirim, Chavantes and Capivara) were selected. Physical, chemical, and biological (phytoplankton and zooplankton) data were obtained in two sampling campaigns carried out in March (wet season) and October (dry season) of 2011. For each reservoir we sampled six stations, arranged on a gradient established between the lotic (Paranapanema River entrance) and lentic (dam) areas. According to the Trophic State Index for tropical/subtropical reservoirs, the sampling stations were categorized between ultraoligotrophic and mesotrophic. Four metrics achieved significant discrimination (out of a set of 20 candidate metrics). The individual metric scores were summed to provide a Planktonic Index of Biotic Integrity score, which ranged as Mesotrophic (4-9), Oligotrophic (10-14) and Ultraoligotrophic (15-20), corresponding to the classification of fair, good and excellent, respectively. Following the longitudinal sequence, Jurumirim was classified as Oligotophic (Good) and both Chavantes and Capivara as Ultraoligotrophic (Excellent). This study demonstrated that the Planktonic Index of Biotic Integrity is a potential tool for monitoring large subtropical reservoirs, as planktonic organisms are sensitive to environmental changes and this index integrates distinct temporal and spatial scales.

Different chemometric approaches were used to determine generic patterns in the temporal and spatial variations in the coastal water quality of the northern Yellow Sea off Yantai, China. Hierarchical cluster analysis grouped the 16 months into two periods (i.e. March-October and November-February), reflecting strong seasonality in the data, and grouped the 12 sampling sites into two clusters (i.e. outside Yantai Bay and inside Yantai Bay), based on similarities in water quality characteristics. Discriminant analysis gave the best results for data complexity reduction during temporal analysis, but not during spatial analysis. Discriminant analysis identified five significant parameters (water temperature, salinity, and concentrations of dissolved inorganic nitrogen, dissolved inorganic phosphate and dissolved silicate) affording about 97.9% correct assignations in temporal analysis. In addition, principal component analysis identified three varifactors that explained 71% of temporal changes in the coastal water quality data set. Overall, the present study showed that these multivariate statistic methods were effective for evaluating temporal and spatial variations in the coastal water quality of Yantai. Water temperature and nutrient inputs may be major driving factors for the trophic status of these coastal waters. Low variances in spatial patterns of water quality parameters of Yantai were mostly related to the unrestricted water exchange between Sishili Bay and the Yellow Sea.

The foodweb of El Tóbari Lagoon (central-east Gulf of California) was studied for four seasons through the carbon and nitrogen isotopic characterization of primary producers, invertebrates, fish, birds and potential food sources. The range of δ¹³C measured was much wider for potential food sources than for consumers. Many organisms presented enrichments of δ¹³C and δ¹⁵N values. There was a clear trend toward increasing δ¹³C and δ¹⁵N from base organisms to top-predators in the four seasons. The isotopic and percentage of contribution data confirmed that suspended particulate organic matter and phytoplankton are the main organic source supporting the foodweb. Our results also imply the occurrence of a nutrient transfer from zooplankton to some invertebrates and juvenile fishes. Consumers were composed in four trophic levels, with trophic level 2 occupied by zooplankton and filter-feeders and trophic level 4 occupied by carnivorous fish and most bird species. Carnivorous fish exhibited dietary similarities by a considerable sharing of resources, which could be related to the abundance of possible prey, between invertebrates and juvenile fishes. Crustaceans and fish represented the main food sources of birds, although some birds showed more dietary variation (marine and offshore prey).

The focus of this study was the temporal and spatial variations of extreme significant wave heights and nearshore return-period wave heights in the South China Sea, based on the wave model and European Reanalysis-Interim data from 1979–2016. Measured buoy data were available from near Yongxing Island for comparison with the reanalysis data during the passage of typhoons. Annual maximum significant wave heights showed a statistically significant increasing trend over most of the South China Sea, whereas statistically insignificant decreasing or increasing trends were observed for seasonal maximum significant wave heights associated with the different characteristics of the typhoon events. Nonstationary generalized extreme value analysis was used to investigate the influence of nearshore extreme significant wave heights derived from the Simulating Waves Nearshore model at four offshore locations in the South China Sea. The fastest increase of 100-year return significant wave heights was found to be 0.0033 m yr^–1 in the western South China Sea. The results show that, in recent decades, no significant variation trends can be found in return-period wave heights at nearshore of South China Sea, which may be related to tracks of intense typhoons in the region.

Resacas of the lower Rio Grande River (secondary channels, distributaries, oxbow lakes) are vital freshwater wetlands under intense anthropogenic pressure. Many of these wetlands have their water levels tightly managed and some are being restored. Reliable bioassessment methods to effectively discriminate among resacas of differing ecological status are needed. Common components of bioassessments for aquatic ecosystems include surveys of biological communities, among which the macroinvertebrates are generally considered the most accurate. The macroinvertebrate community of resacas is virtually undocumented and various sampling methods have never been used in parallel. Here we used two popular sampling techniques (benthic corer and dip net), while producing the first portrait of the macroinvertebrate community inhabiting resacas. Despite sampling different invertebrate assemblage subsets, both methods discriminated among studied resacas in a similar manner; however, the corer presents several advantages including: 1) a much higher precision (based on coefficients of variation), 2) more adequate representation of an indicator species (invasive gastropod), and 3) clearer differences in functional feeding groups among resacas which constitutes an additional indicator metric.

This study was conducted to assess the recruitment rate of coral spats and other invertebrates near to the coral reef ecosystem of Gulf of Mannar. The reef region examined was at Kurusadai Reef Complex (Gulf of Mannar) for this assessment. There were two sets of invertebrate settlement tripods deployed and exposed at a depth of 2m. Seventy two settlement tiles measuring 20x20cm in two different angles were fixed in these tripods in the benthic reef ecosystem. In order to assess the impact of Sea surface temperature on the invertebrate settlement, Onset Hobo Pendant® Temperature logger was also attached with the tripods. The sediment traps in duplicate were also erected in the study site to assess the sedimentation rate of the reef ecosystem. About 80% of recruited coral spats were observed on the tiles which were exposed at 60° angle. Principal component analysis also supported that the most influencing species were coral spats followed by barnacles and bivalves in the 60° angle exposed settlement tiles. It was also observed that the most influencing place of coral spats' recruitment was on the inner tiles. The mean sedimentation rate observed was 14.6±4.8mg.cm^–2.d^–1. The lower density of coral spats observed on 90° and 60° angle exposed outer tiles might be due to the observed sedimentation rate and it is believed that coral spats preferred the shaded environment initially for further perpetuation in the environment. Moreover, Bray-Curtis cluster analysis supported that the coral spats found on the inner tiles having 80% similarity in this assessment. The coral spats found in this assessment were species from Pocilloporidae and Poritidae.

The relationship between zooplankton community structure and selected environmental conditions was investigated by simultaneous two-day consecutive sampling in the waters overlying coral and sand sites off Sibu Island and a seagrass site off Tinggi Island, Johor, Malaysia. A total of 129 taxa were identified, 60 non-copepod taxa and 69 copepod species in all samples. Uni- and multi-variate analyses reveal distinct coral, sand, seagrass copepod assemblages with indicator copepod species and attributes of their size fractions. Small fraction (100–335 µm) samples contained greatest number of individuals, few rare species and were densest at onshore depths, and the opposite for large fraction (>335 µm) samples but were densest at nighttime and most species rich in the coral site at night. Higher species diversity at offshore stations is due likely to ecotonal effects of overlapping oceanic and nearshore communities. This study demonstrates the usefulness of uni- and multi-variate analyses in identifying patterns in zooplankton community structure in representative shallow tropical habitats, and the need for accurate zooplankton taxonomy, nighttime and daytime and onshore and offshore sampling, and size fractionation of samples.