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Mangrove ecosystem responses to tropical cyclones have been well-documented over the last half century. Variability in tree mortality, aboveground biomass accumulation, canopy closure, and subsequent recovery has been explained by species, size, and geomorphology. This study gauges the initial response and short-term recovery of Puerto Rico’s mangroves following the 2017 hurricane season. Survival probability of tagged trees decreased with time, and the mean mortality across all sites was 22% after eleven months. Mean canopy closure loss was 51% one month after the hurricanes, and closure recovery rates decreased with time following the storms. Aboveground biomass accumulation decreased by 3.5 kg yr−1 per tree, corresponding to a reduction of 8.6 Mg ha−1 yr−1 at the stand level. Eleven months later, the mangroves recovered to 72% canopy closure and to nearly 60% of their pre-storm growth rates. Species, size, and geomorphology were found to play a role, while an influence of surrounding land cover and urbanization could not be detected. Larger trees suffered 25% more mortality than smaller size classes, and Laguncularia racemosa suffered 11% less mortality than other species. Forests in tidally restricted canals experienced more canopy loss but faster recovery than open embayment systems. Canopy closure for some forests is not forecasted to return to pre-storm levels in the next 20 years, which when combined with changes in hurricane frequencies may or may not be sooner than the next extreme hurricane disturbance. These findings suggest that size, species, and geomorphology are important in mangrove resilience to tropical storms and that urbanization does not play a role. Managing mangrove ecosystems for optimal shoreline protection will depend upon knowing which forests are at greatest risk in a future of changing tropical cyclone strength and frequency.

Spatial subsidies and habitat connectivity are critical factors in estuarine trophic webs. Advection and tidal dispersion of organic matter including plankton from productive regions such as wetlands can subsidize consumers in less productive areas. These dispersive fluxes have generally been assumed to result from tidal mixing along concentration gradients, but other mechanisms of dispersion may be important. We estimated fluxes of the calanoid copepod Pseudodiaptomus forbesi between a restored marsh and a connected channel in the northern San Francisco Estuary in summer 2018 using continuous flow data and hourly abundance data over four tidal cycles. Late copepodites and adults were demersal, abundant in the water column only at night, and abundance was uncorrelated with tidal flows. Over the tidal day, dispersive fluxes of copepods were variable. However, over the entire summer, tidal flows were flood dominant at night when the copepods were in the water column, driving an estimated dispersive flux into the marsh. Dispersion at the marsh will change seasonally as tidal patterns and copepod abundance change. Our results show that the transport of zooplankton in shallow tidal systems is regulated by the interactions of diel zooplankton behavior with long-term tidal patterns. Similar interactions in other systems will result in transport based on site-specific hydrodynamics and zooplankton behavior, and could move zooplankton up the concentration gradient rather than down. Patterns of zooplankton behavior and currents occur on a wide variety of time scales; thus, researchers must take a long-term perspective to understand these interactions.

This paper describes the results of 10 years of water quality monitoring in the Indian River Lagoon Florida, with special emphasis on the relationships between trends in climatic conditions and the distribution, composition, and abundance of the phytoplankton community. The Indian River Lagoon, which spans 220 km of Florida’s east coast, is a region of particular concern because of the rapid rate of human development throughout the region and the hydrologically restricted character of the lagoon, which heightens the potential for algal bloom. Water sampling was carried out on a monthly to twice-monthly basis at six sites located in the northern and central lagoon. The 10-year study included both extended periods of below and above average rainfall. A number of ecologically distinct regions exist within the lagoon, which differ considerably in water exchange properties and watershed inputs. The northern lagoon is characterized by longer water residence times, lower phosphorus concentrations, higher nitrogen concentrations, and more stable salinity conditions than the central lagoon. Mean phytoplankton biovolumes were substantially higher at the sites in the northern lagoon than at the sites in the central lagoon, and algal blooms were more common and intense in the former region. Inter-annual patterns of phytoplankton biovolume were also different in the northern and central lagoon. In the northern lagoon, phytoplankton biovolumes were lowest during the drought period, from the autumn of 1998 to the spring of 2001. By contrast, algal bloom events in the central lagoon were not only less frequent but were not tied to periods of high rainfall. The most widespread and common bloom formers were the potentially toxic dinoflagellate Pyrodinium bahamense var. bahamense and two centric diatoms, Dactyliosolen fragilissimus and Cerataulina pelagica. Many of the biovolume peaks observed over the study period were attributable to these three species. The results of time series modeling of phytoplankton dynamics further highlighted the disparities between the two regions of the lagoon in terms of the suite of parameters that best predict the observed trends in the biomass of phytoplankton. Overall, the outcome of this initial modeling effort in the Indian River Lagoon suggests that time series approaches can help define the factors that influence phytoplankton dynamics.

Puget Sound is an estuarine inland sea fed by 14 major rivers and also strongly influenced by the nearby Fraser River. A comprehensive, particle-based reanalysis of an existing circulation model was used to map the area of influence of each of these rivers over a typical seasonal cycle. Each of the 131,000 particles released in the 15 rivers was associated with a freshwater volume, a nutrient load, and a fecal coliform load based on statistics from 10 years of Washington Department of Ecology monitoring data. Simple assumptions regarding mortality and nutrient utilization/export rates were used to estimate the decrease in bacterial and nutrient load as individual parcels of river water age. Reconstructions of basin-scale volume fluxes and salinities from the particle inventory provide consistency checks on the particle calculation, according to methods suitable for error analysis in a wide range of particle-based estuarine residence time studies. Results suggest that river contributions to total freshwater content in Puget Sound are highly nonlocal in spring and summer, with distant, large rivers (the Fraser and Skagit) accounting for a large fraction of total freshwater. However, bacterial mortality and nutrient export rates are relatively fast compared with transport timescales, and so significant loadings associated with major rivers are in most cases only seen close to river mouths. One notable exception is fecal coliform concentration in Bellingham Bay and Samish Bay, which lie north of Puget Sound proper; there, it appears that the Fraser River may rival local rivers (the Samish and Nooksack) as a pathogen source, with the much higher flow volume of the Fraser compensating for its remoteness.

The complex interaction of a daily temporally fixed sampling design with seasonal, tidal, and diurnal cycles can result in serious aliasing and reduced usefulness of estuarine data. The choice of appropriate sampling windows for data grouping and analysis of tidally influenced data is complex and must take into account both solar and lunar influences and their interactions in order to represent actual estuarine conditions. A fixed modulus for grouping or time-series analysis introduces errors. Grouping data by calendar month can be misleading since calendar months may have as many as three or as few as one spring tide. Daily measurements of salinity and water clarity at a fixed time of day were analyzed to illustrate the effects of aliasing. Although the length of synodical (lunar) months is also variable, a seasonally adjusted grouping variable based on solar and synodical month (MO-DAY), created to partially correct for aliasing, was found to be an efficient way to remove short-term cycles for the identification of long-term trends, episodic events, and spatial patterns.

We utilized an extensive data set (1977–2013) from a water quality monitoring program to investigate the recovery of a Danish estuary following large reductions in total phosphorus (TP) and total nitrogen (TN) loading. Monthly rates of net transport and biogeochemical transformation of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) were computed in two basins of the estuary using a box model approach, and oxygen-based rates of net ecosystem production (NEP) were determined. Since 1990, nutrient loading was reduced by 58 % for nitrogen and 80 % for phosphorus, causing significant decreases in DIN (60 %) and DIP (85 %) concentrations. Reductions in nutrient loadings and concentrations reduced annual chlorophyll levels by 50 % in the inner estuary and improved Secchi depth by approximately 1 m during the same period, particularly in the summer period. In the outer, deeper region of the estuary trends in water quality was less evident. Improvements in the inner estuary were strongly coupled to declines in DIN. Thresholds of DIN and DIP concentrations limiting phytoplankton growth indicated that both regions of the estuary were nitrogen limited. NEP rates indicated the development of more net autotrophic conditions over time that were likely associated with higher benthic primary production stimulated by improved light conditions. Box model computations revealed a modest reduction in summer net production of DIP over time, despite the persistence of elevated fluxes for several years after external loads were reduced. Since the mid-1990s, nutrient loading and transformation were stable while nutrient concentrations continued to decline and water quality improved in the inner estuary. The oligotrophication trajectory involved an initial fast transformation and modest retention of nutrients followed by a gradual decline in the rate of improvement towards a new stable condition.

Barataria (LA, USA) is an interdistributary deltaic basin that has experienced extensive marsh loss. The fate of these marshes is strongly controlled by the concentration of total suspended sediments (TSS) in the adjacent open bay water. This parameter, however, is poorly constrained, thus limiting the ability to predict the future marsh evolution. Here we investigate the open bay water sediment dynamics using three complementary approaches: monthly field surveys at 37 locations along the bay axis over 22 years, remote sensing over 20 years, and turbidity time series at 5 locations over 4 years. Monthly field sampling and remote sensing reveal that the TSS is highly seasonal and spatially variable. In particular, the sediment delivered through the Gulf Intracoastal Waterway (GIWW) during the flood season (January–April) dominates the TSS signal in mid-Barataria. This sediment originates mainly from the Atchafalaya River and is advected for more than 100 km before reaching Barataria. Because of a hysteresis in sediment transport, the TSS in the river water, and hence in the GIWW, is not uniquely related to the river discharge. As such, late flood season discharges do not contribute much sediment to Barataria. We estimate that the GIWW delivers on average 0.21 Tg of sediment per year to mid-Barataria. A different sediment input is instead present in lower Barataria, where river-borne sediment exiting the “birdfoot” of the Mississippi Delta is advected by easterly winds, especially during spring. At all five stations within Barataria, turbidity time series reveal that the daily sediment dynamics is mainly associated with local wind wave resuspension. River inputs and wave resuspension contribute nearly equally to the yearly averaged TSS, of about 80 mg/l on average. The GIWW, built in the 1920s, is an important but overlooked source of sediments for Barataria that can serve as a present-day analogue for the proposed Mississippi River sediment diversions.

Remote sensing imagery can be an invaluable resource to quantify land change in coastal wetlands. Obtaining an accurate measure of land change can, however, be complicated by differences in fluvial and tidal inundation experienced when the imagery is captured. This study classified Landsat imagery from two wetland areas in coastal Louisiana from 1983 to 2010 into categories of land and water. Tide height, river level, and date were used as independent variables in a multiple regression model to predict land area in the Wax Lake Delta (WLD) and compare those estimates with an adjacent marsh area lacking direct fluvial inputs. Coefficients of determination from regressions using both measures of water level along with date as predictor variables of land extent in the WLD, were higher than those obtained using the current methodology which only uses date to predict land change. Land change trend estimates were also improved when the data were divided by time period. Water level corrected land gain in the WLD from 1983 to 2010 was 1 km2 year−1, while rates in the adjacent marsh remained roughly constant. This approach of isolating environmental variability due to changing water levels improves estimates of actual land change in a dynamic system, so that other processes that may control delta development such as hurricanes, floods, and sediment delivery, may be further investigated.

Floods are extreme weather events that can rapidly change water quality in receiving estuaries. The delivery of nutrients to the coastal zone via floods may stimulate productivity; however, in urban areas, the degradation of water quality and influx of contaminants can negatively affect inhabiting biota. Determining flood effects on inhabiting biota is important for informing catchment management practices. We investigated the body condition response of a commercially important prawn species, the brown tiger prawn Penaeus esculentus, to a large cyclone-driven flood in an urbanized subtropical coastal bay. Prawns were caught 10 days before the flood, 11 days after the flood, and 53 days after the flood in bare substrate areas of central Moreton Bay in Australia. Stable isotopes (δ15N and δ13C) were determined for prawn muscle tissue, and lipid content and a length-weight (Fulton’s K) index were used to assess prawn body condition. There were two distinct isotope signatures of tiger prawns living in either riverine or marine influenced areas, suggesting different residency areas within the bay. A flood signal (lower δ13C values post-flood) was detected in prawns in the southern area closest to the Logan River. Condition indices showed a short-term increase in condition of prawns in these southern sites, with no apparent condition change in prawns at other sites. A concurrent pulse in benthic primary productivity (chlorophyll a biomass) was measured in this southern area. Our results suggest that nutrients from the flood stimulated benthic primary production that was transferred through the food web, with positive impacts on prawn nutrition at southern sites. With an expected increase in unpredictable weather, including floods, under a changing climate, understanding short- and long-term ecosystem responses in modified catchments is important for mitigating sediment erosion and estuarine and coastal infilling effects, while maintaining productivity benefits to fisheries in receiving estuaries.