Inland Bays Research Articles

Development of a Reference Transcriptome and Identification of Differentially Expressed Genes Linked to Salt Stress in Salt Marsh Grass (Sporobolus alterniflorus) along Delaware Coastal Regions.

Salt marsh grass (Sporobolus alterniflorus) plays a crucial role in Delaware coastal regions by serving as a physical barrier between land and water along the inland bays and beaches. This vegetation helps to stabilize the shoreline and prevent erosion, protecting the land from the powerful forces of the waves and tides. In addition to providing a physical barrier, salt marsh grass is responsible for filtering nutrients in the water, offering an environment for aquatic species and presenting a focal point of study for high salt tolerance in plants. As seawater concentrations vary along the Delaware coast from low to medium to high salinity, our study seeks to identify the impact of salt tolerance in marsh grass and to identify genes associated with salt tolerance levels. We developed more than 211,000 next-generation-sequencing (Illumina) transcriptomic reads to create a reference transcriptome from low-, medium-, and high-salinity marsh grass leaf samples collected from the Delaware coastline. Contiguous sequences were annotated based on a homology search using BLASTX against rice (Oryza sativa), foxtail millet (Setaria italica), and non-redundant species within the Viridiplantae database. Additionally, we identified differentially expressed genes related to salinity stress as candidates for salt stress qPCR analysis. The data generated from this study may help to elucidate the genetic signatures and physiological responses of plants to salinity stress, thereby offering valuable insight into the use of innovative approaches for gene expression studies in crops that are less salt tolerant.

Saltwater intrusion increases phosphorus abundance and alters availability in coastal soils with implications for future sea level rise

Sea level rise (SLR) promotes saltwater intrusion (SWI) into coastal soils globally at an increasing rate, impacting phosphorus (P) dynamics and adjacent water quality. However, how SWI influences P molecular speciation and availability in coastal soils remains poorly understood. By using a space-for-time substitution strategy, we evaluated the SWI impacts on P transformation along a SWI gradient at the Rehoboth Inland Bay, which consists of five sampling locations along a transect representing different SWI degrees. Soils were analyzed at the macro- and micro-scale using X-ray absorption near edge spectroscopy (XANES) and the modified Hedley fractionation. With increasing distance from the Bay, soil salinity (29.3–0.07 mmhos cm−1), the proportion of Fe3+ to total Fe, and P concentrations decreased. The fractionation showed that recalcitrant P was dominant (86.9–89.5% of total P). With increasing SWI, labile P increased gradually, reached a plateau, and then decreased sharply. Bulk XANES spectroscopy showed that soil P was likely dominated by iron and aluminum-associated P (Fe/Al-P), regardless of the SWI degree. Hence, with increasing SWI, P increasingly accumulated in a recalcitrant pool, mainly as Fe/Al-P. μ-XANES spectroscopy revealed that calcium-associated P (Ca-P) existed in P-rich spots of the greatest SWI soil while Al-P occurred in P-rich spots of the low SWI soil, consistent with the greater HCl-P (presumably Ca-P) in the former soil. Overall, results demonstrate that SWI impacts P availability and environmental risk in coastal soils depending on the degree of SWI. These findings have important implications for understanding soil P cycling and availability in SLR-impacted coastal areas.

Climate change impact on hurricane storm surge hazards in New York/New Jersey Coastlines using machine-learning

Recent hurricane losses in the New York Metropolitan area demonstrate its vulnerability to flood hazards. Long-term development and planning require predictions of low-probability high-consequence storm surge levels that account for climate change impacts. This requires simulating thousands of synthetic storms under a specific climate change scenario which requires high computational power. To alleviate this burden, we developed a machine learning-based predictive model. The training data set was generated using a high-fidelity hydrodynamic model including the effect of wind-generated waves. The machine learning model is then used to predict and compare storm surges over historical (1980–2000) and future (2080–2100) periods, considering the Representative Concentration Pathway 8.5 scenario. Our analysis encompassed 57 locations along the New York and New Jersey coastlines. The results show an increase along the southern coastline of New Jersey and inside Jamaica, Raritan, and Sandy Hook bays, while a decrease along the Long Island coastline and inland bays.

Water Level Fluctuations in the Middle and Late Holocene in the Curonian Lagoon, Southeastern Baltic: Results of the Macrofossil and Phytolith Analyses

This paper presents the results of a study on fluctuations in the water level of the Curonian Lagoon (in the Baltic Sea). To date, the genesis of this inland bay as part of the complex postglacial development of the southeastern Baltic is poorly understood. The data from lithological, geochronological, and phytolith analyses, as well as assessments of plant and animal macroremains from the lagoonal sediments, provide a reconstruction of local coastal biocenoses and water level dynamics in the Middle and Late Holocene time. This study reveals the fairly dynamic evolution of the coastal zone of the Curonian Lagoon over the past 7000 years, as indicated by the traced succession of plant communities from forest to near-shore, open-water biocenoses and the alternations of the drying out and inundation of the area under consideration. Thus far, a connection with two stages of the Baltic Sea water level fluctuations has been traced: the regressional stage, which took place approximately 5600 cal years BP, and the Late Subatlantic transgression, which started at approximately 1100 cal BP. This study demonstrates that phytolith (microbiomorphic) analysis is a promising method for the study of temperate-latitude lagoonal sediments, providing information not only on the local plant communities, but also on the changes in the hydrological regime of the area.

Heterosigma akashiwo does not serve as prey and chloroplast donor for the toxic dinoflagellate, Dinophysis acuminata

In laboratory culture, the toxic dinoflagellate Dinophysis acuminata acquires plastids from the ciliate, Mesodinium rubrum, which, in turn, acquires plastids from the cryptophyte, Teleaulax amphioxeia. Reports of D. acuminata from field samples found plastids of the raphidophyte, Heterosigma akashiwo within D. acuminata cells, suggesting a broader range of prey. Dinophysis blooms often co-occur with H. akashiwo in Delaware's inland bays. In the study presented here, predation on H. akashiwo by D. acuminata was investigated. Growth rates of D. acuminata were measured when cultured with H. akashiwo either alone or with its known prey, M. rubrum. M. rubrum was also cultured with H. akashiwo to examine predation by the ciliate as a vector for Heterosigma plastids. Ingestion rates by D. acuminata were measured when presented with H. akashiwo as prey, and retention of plastids from H. akashiwo was investigated by measuring chlorophyll a fluorescence intensities in D. acuminata cells presented with H. akashiwo as prey compared to M. rubrum. Additionally, a fluorescence-based method was developed to identify the presence of the accessory pigment fucoxanthin from H. akashiwo plastids in cells of D. acuminata. Results showed that the growth rate of D. acuminata was significantly lower when offered H. akashiwo as prey compared the growth rate when offered M. rubrum as prey. Likewise, no predation was observed when D. acuminata was offered H. akashiwo as prey. Intensity of chlorophyll a fluorescence was lower when H. akashiwo was offered as prey compared to M. rubrum, and fucoxanthin was not detected in any of the Dinophysis cells examined after incubation with H. akashiwo. Results of this investigation do not support the hypothesis that D. acuminata preys on H. akashiwo and highlight the need for further research on factors that stimulate the growth of Dinophysis in field populations.

Temporal Changes in Delaware Waters Using Long-Term (1967–2019) Water Temperature Data

The present article provides long-term (1967–2019) water temperature data collected from Delaware water quality monitoring sites. In Delaware, there are approximately 140 water quality monitoring sites in Piedmont, Delaware Bay, Chesapeake Bay, and Inland Bay drainage basins. Long-term quarterly (i.e., four times a year: Q1—January–February–March; Q2—April–May–June; Q3—July–August–September; Q4—October–November–December) water temperature data were calculated from each water quality monitoring sites’ continuous monthly data. This study focuses on water quality monitoring sites with significant (p-value identifying linear regression model) increasing or decreasing trends of water temperature. Quarterly water temperature data, statistical analysis, and maps showing increasing and decreasing trend from water quality monitoring sites with significant trends are presented in this article.

Responses of Free-Living Vibrio Community to Seasonal Environmental Variation in a Subtropical Inland Bay.

Vibrio are widely distributed in aquatic environments and strongly associated with eutrophic environments and human health through the consumption of contaminated seafood. However, the response of the Vibrio community to seasonal variation in eutrophic environments is poorly understood. In this study, we used a Vibrio-specific 16S rRNA sequencing approach to reveal the seasonal distribution pattern and diversity of the Vibrio community in the Maowei Sea, Beibu Gulf of China. The Shannon diversity of the Vibrio community was highest in the summer, while β-diversity analysis showed that Vibrio community structures were significantly different between seasons. Distance-based redundancy analysis (dbRDA) and Mantel test analysis suggested that total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), dissolved inorganic nitrogen (DIN), salinity, and temperature were the key environmental factors shaping the Vibrio community structure, indicating a strong filtering effect of trophic condition on Vibrio communities. Furthermore, through random forest analysis, V. fluvialis, V. alginolyticus, V. proteolyticus, V. splendidus, and the other eight Vibrio species were more sensitive to eutrophic changes. This study revealed seasonal changes in Vibrio communities and the influence of environmental variation on Vibrio community composition, contributing to a better understanding of their potential ecological roles in a subtropical inland bay.

Analysis and prediction of storm water levels in Delaware inland bays

A simple approach based on an analytical model and available tide gauge data is proposed for the analysis of storm tide damping inside inland bays with complex bathymetry and for the prediction of peak water levels at gauge locations during storms. The approach was applied to eight tide gauges in the vicinity of inland bays in Delaware. Peak water levels at the gauge locations were analyzed for 34 storms during 2005-2017. A damping parameter in the analytical model was calibrated for each bay gauge. The calibrated model predicted the peak water levels within errors of about 0.2 m except for Hurricane Sandy in 2012. The analytical model including wave overtopping was used to estimate the peak wave overtopping rate over the barrier beach from the measured peak water level in the adjacent bay.

Ice entrapment mortality may slow expanding presence of Arctic killer whales

Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic during the summer months. Increasing killer whale sightings throughout the region, and incursions into areas where they have not historically been observed, have been linked with declining sea ice, which has raised questions about the potential ecological impacts of a greater killer whale presence in the Arctic. Here we report on four killer whales that died of starvation after overwintering in southeastern Hudson Bay. This incident is similar to two other reported killer whale ice entrapments in Hudson Bay in 2011 and 2013, which together exceed the incidence of such events over the previous century. The six confirmed, and up to 16 more assumed, deaths due to ice entrapments over the past decade almost certainly represent significant levels of mortality for the population(s) of killer whales in the Canadian Arctic. Ice entrapments of naive killer whales exploring new Arctic territory may therefore offer a natural check on range expansions in the region, particularly in convoluted inland bays and inlets into which they pursue previously inaccessible prey, but fail to exit prior to ice formation.

LONG-TERM SUBSIDENCE OF BEACH NOURISHMENT AND DUNE RESTORATION IN CAMINADA HEADLANDS, COASTAL LOUISIANA

Coastal barrier islands are the first line of defense for protecting wetlands, inland bays, and mainland regions from direct effects of wind, waves, and storms. Rosati (2006) indicate that 20 to 40% of the total sand volume can be sequestered and lost from the sandy barrier island through consolidation. As a result, predicting long-term subsurface sediment consolidation is integral to determining the ability of barrier islands to provide coastal protection and resilience to future hazards, such as relative sea level rise, sediment erosion, and hurricanes. This study uses the Caminada Headlands geotechnical investigations and monitoring data to determine empirical correlations for deltaic sediment compressibility and develop a validated and calibrated consolidation and subsidence numerical model for future barrier island restoration projects. With this calibrated model, differential settlements associated with sand fill placement can be estimated to design placement elevations to maintain post-construction topography for ecological habitat and restoration requirements and can be used for future beach restoration projects along barrier island shorelines.

PREDICTION OF SMALL BAY FLOODING THROUGH TIDAL INLET AND BY WAVE OVERTOPPING OF BARRIER BEACH

Low-laying barrier beach is easily overtopped by waves during a severe storm, resulting in increased water level in the inland bays and extensive flooding along the long bay shoreline. Kobayashi and Zhu (2017) developed a simple analytical model to predict bay peak still-water elevation in Indian River Bay and Rehoboth Bay for given ocean peak still-water elevation and surge duration at Lewes . 27 storms identified during 2005-2015 were used to calibrate the dimensionless parameter K* related to the inlet and bay characteristics. The agreement is within 10% at tide gauges I and R and within 30% at tide gauge D.

Growth and reproductive ecology of the portunid crab Charybdis japonica in an open seacoast and an inland bay in Fukuoka, Japan

Growth and reproductive ecology of the portunid crab Charybdis japonica in an open seacoast and an inland bay in Fukuoka, Japan

Treatment effects during the post-operative care on the rate of pearl-sac formation in the pearl oyster Pinctada fucata

The pearl culture industry using the Akoya pearl oyster Pinctada fucata in Japan has been suffering from low productivity due to the proportion of low-quality pearls, which are not round in shape and have blemishes on the surface, is fairly high with over 70% of pearls effected. Recent studies indicate that the immersion treatment of oysters in low salinity seawater (25psu) in a tank for 8days just after the implantation of nuclei has a positive effect on the production of high-quality pearls compared to the suspension of oysters in the sea (33psu), so-called the “conventional method”, throughout two weeks of the post-operative care. However, a mechanism to increase the proportion of high-quality pearls in low salinity seawater is not fully known. In this study, we compared the periods from the implantation of nuclei to the completion of pearl-sac formation among implanted pearl oysters nursed in tanks containing low salinity (25psu) or normal salinity (33psu) seawater in tanks and in the sea (33psu). After the immersion of the implanted oysters in 25 or 33psu seawater in the tanks for 8days, animals were suspended from a raft in an inland bay for the remainder of post-operative care period. The implanted oysters treated with the conventional method were all fastened from the raft throughout the post-operative care period. The oysters from the three treatments were 10% formalin-fixed at periodic intervals and thin slices of the nucleus-implanted part of body were prepared for the examination of the process of pearl-sac formation. The oysters suspended from the raft in the sea throughout the post-operative care period showed the shortest interval from the implantation to the pearl-sac formation, followed by those in normal salinity and low salinity treatments, respectively. This trend corresponds well to that in the proportion of high-quality pearls among the three treatments. The results of the present study suggest that the delay of pearl-sac formation is most likely one of the important factors in preventing deformities and blemishes of pearls in future culture production.

Spatial and temporal variation in abundance, group size and behaviour of bottlenose dolphins in the Florida coastal Everglades

Bottlenose dolphins (Tursiops truncatus) are abundant in many coastal ecosystems, including the coastal Everglades. Understanding spatial and temporal variation in their abundance and group sizes is important for estimating their potential ecological importance and predicting how environmental changes (e.g. ecosystem restoration) might impact their populations. From August 2010 to June 2012, we completed a total of 67 belt transects covering a total of 2650 linear km and an area of 1232 km2. Dolphin densities varied spatially and temporally. The highest densities of dolphins were found in coastal oceans and inland bays and were lowest in rivers. Use of rivers, however, increased during the dry season while densities in other habitats remained similar across seasons. Dolphins appeared to prefer portions of bays close to mangrove-covered islands over open waters. A resighting rate of 63.6% of individuals across the 2-year study suggests that at least a portion of the population is probably resident within study regions over long time periods. The largest groups (mean 6.28, range 1–31) were found in open waters and bays despite apparently low predation pressure. Indeed, shark bite scars – likely the result of unsuccessful predation attempts – were conclusively observed on only 1% of individuals. Although further studies are warranted, the high densities of dolphins suggest that they are an important upper trophic level predator in the coastal Everglades, but their ecological importance probably varies in space and time.

Effects of Microbial and Heavy Metal Contaminants on Environmental/Ecological Health and Revitalization of Coastal Ecosystems in Delaware Bay

The presence of heavy metals, excess nutrients, and microbial contaminants in aquatic systems of coastal Delaware has become a public concern as human population increases and land development continues. Delaware's coastal lagoons have been subjected to problems commonly shared by other coastal Mid-Atlantic states: turbidity, sedimentation, eutrophication, periodic hypoxic/anoxic conditions, toxic substances, and high bacterial levels. The cumulative impact of pollutants from run-off and point sources has degraded water quality, reduced the diversity and abundance of various fish species, invertebrates, and submerged aquatic vegetation. The effects are especially pronounced within the manmade dead end canal systems. In this article, we present selected case studies conducted in the Delaware Inland Bays. Due to the ecological services provided by bivalves, our studies in Delaware Inland Bays are geared towards oysters with special focus on the microbial loads followed by the water quality assessments of the bay. The relationships between oysters (Crassostrea virginica), microbial loads and nutrient levels in the water were investigated. The heavy metal levels monitored near the waste water treatment plant in the inland bays are marginally higher than the recommended EPA limits Also, our studies confirmed that aerobic bacteria and Vibrionaceae levels are salinity dependent. Total bacteria in oysters increased when nitrate and total suspended solids increased in the waters. Studies such as these are important because every year millions of Americans consume raw oysters. Data collected over the last ten years from our studies may be used to build a predictive index of conditions that are favorable for the proliferation of human pathogenic bacteria. Results from this study will benefit the local community by helping them understand the importance of oyster aquaculture and safe consumption of oysters while making them appreciate their ecological and commercial values. This will also be of tremendous help to the commercial shellfish aquaculture farms to predict poor conditions to prevent oysters’ consumption when bacterial levels are high in water.

Chlorinated polycyclic aromatic hydrocarbons in surface sediment from Maowei Sea, Guangxi, China: occurrence, distribution, and source apportionment.

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) with three to five aromatic rings have been documented to ubiquitously occur in environmental matrices. In this study, residual concentrations and profiles of 20 individual ClPAHs were determined in 35 surface sediment samples from Maowei Sea, a semi-enclosed shallow inland bay located in the northwestern part of South China Sea. The concentrations of ΣClPAHs in sediment ranged from 313 to 9650pg/g dw with a detection rate of 43-100%. Of the individual ClPAH congeners, 9-ClPhe was the most abundant in Maowei Sea with the concentrations that ranged from 99.9 to 3610pg/g dw (mean 1120pg/g dw). High-molecular-weight ClPAH congeners (four to five rings) were predominant in sediments from sampling locations near a petrochemical industrial complex, whereas low-molecular-weight ClPAH congeners (three rings) were predominant in sediments from estuarine and mangrove locations. A positive matrix factorization (PMF) model in combination with dioxin-like toxic equivalency quotient (TEQ) results was used to apportion sources of ClPAHs. Vehicular emission, combustion/chemical industrial processes, and two other unknown sources accounted for 40.1, 25.5, 20.8, and 13.6%, respectively, of ClPAH sources in sediment; their contribution to TEQs in sediments were 24.2, 40.5, 19.3, and 16.0%, respectively. Further investigations are needed to elucidate potential sources and ecological risks of ClPAHs in sediments.

Hydrogeologic controls on groundwater discharge and nitrogen loads in a coastal watershed

Summary Submarine groundwater discharge (SGD) is a small portion of the global water budget, but a potentially large contributor to coastal nutrient budgets due to high concentrations relative to stream discharge. A numerical groundwater flow model of the Inland Bays Watershed, Delaware, USA, was developed to identify the primary hydrogeologic factors that affect groundwater discharge rates and transit times to streams and bays. The distribution of groundwater discharge between streams and bays is sensitive to the depth of the water table below land surface. Higher recharge and reduced hydraulic conductivity raised the water table and increased discharge to streams relative to bays compared to the Reference case (in which 66% of recharge is discharged to streams). Increases to either factor decreased transit times for discharge to both streams and bays compared to the Reference case (in which mean transit times are 56.5 and 94.3 years, respectively), though sensitivity to recharge is greater. Groundwater-borne nitrogen loads were calculated from nitrogen concentrations measured in discharging fresh groundwater and modeled SGD rates. These loads combined with long SGD transit times suggest groundwater-borne nitrogen reductions and estuarine water quality improvements will lag decades behind implementation of efforts to manage nutrient sources. This work enhances understanding of the hydrogeologic controls on and uncertainties in absolute and relative rates and transit times of groundwater discharge to streams and bays in coastal watersheds.

Community-Level and Species-Specific Associations between Phytoplankton and Particle-Associated Vibrio Species in Delaware's Inland Bays.

Vibrio species are an abundant and diverse group of bacteria that form associations with phytoplankton. Correlations between Vibrio and phytoplankton abundance have been noted, suggesting that growth is enhanced during algal blooms or that association with phytoplankton provides a refuge from predation. Here, we investigated relationships between particle-associated Vibrio spp. and phytoplankton in Delaware's inland bays (DIB). The relative abundances of particle-associated Vibrio spp. and algal classes that form blooms in DIB (dinoflagellates, diatoms, and raphidophytes) were determined using quantitative PCR. The results demonstrated a significant correlation between particle-associated Vibrio abundance and phytoplankton, with higher correlations to diatoms and raphidophytes than to dinoflagellates. Species-specific associations were examined during a mixed bloom of Heterosigma akashiwo and Fibrocapsa japonica (Raphidophyceae) and indicated a significant positive correlation for particle-associated Vibrio abundance with H. akashiwo but a negative correlation with F. japonica. Changes in Vibrio assemblages during the bloom were evaluated using automated ribosomal intergenic spacer analysis (ARISA), which revealed significant differences between each size fraction but no significant change in Vibrio assemblages over the course of the bloom. Microzooplankton grazing experiments showed that losses of particle-associated Vibrio spp. may be offset by increased growth in the Vibrio population. Moreover, analysis of Vibrio assemblages by ARISA also indicated an increase in the relative abundance for specific members of the Vibrio community despite higher grazing pressure on the particle-associated population as a whole. The results of this investigation demonstrate links between phytoplankton and Vibrio that may lead to predictions of potential health risks and inform future management practices in this region.

Beach response to a fixed sand bypassing system

Indian River Inlet is located at roughly the mid-point of the Atlantic coast of Delaware and connects the ocean to two Delaware inland bays. Jetties constructed in 1940 have maintained the inlet for navigation purposes but have also acted as a barrier to net northerly alongshore sediment transport causing downdrift erosion. A mobile, land-based bypassing system was initiated in 1990 in an effort to counteract this erosion. Beach profile data from 1985 (pre-bypassing) until 2008 are used to investigate the effect of the sand bypassing system on beaches adjacent to the inlet. The downdrift beach experienced horizontal shoreline erosion between 10 and 60m during the pre-bypassing period but accreted 10–20m during the bypassing period. The mean shoreline location on the updrift beach during bypassing is 10–20m landward (erosion) of its position during the pre-bypassing period. Empirical orthogonal function (EOF) amplitudes from analyses performed on mean-removed elevation surfaces during the periods of highest bypassed volume (average of 83% of design rate) showed that the influence of the bypassing system on the downdrift beach extends to about 1500m of the inlet. An EOF analysis showed that different morphologic responses were evident following the initiation of bypass operations. Temporal variations of shoreline and beach morphology were correlated to the temporal variations in bypassing rates on the downdrift beach only. The downdrift beach response was greatest near the inlet for larger bypassing volumes. Correlation in these instances occurred with a roughly 1-year time lag suggesting that the beach quickly redistributes the bypassed sand. EOF amplitude and shoreline response are weakly correlated to bypassed volumes when the system bypassed smaller volumes (average of 56% of design rate) of sand suggesting that there is a minimum bypassing rate, regardless of yearly variability, below which the effect on the downdrift beach is obscured.

Shoreline changes and high-energy wave impacts at the leeward coast of Bonaire (Netherlands Antilles)

Supralittoral coarse-clast deposits along the shores of Bonaire (Netherlands Antilles) as well as increased hurricane frequency during the past decade testify to the major hazard of high-energy wave impacts in the southern Caribbean. Since deducing certain events from the subaerial coarse-clast record involves major uncertainties and historical reports are restricted to the past 500 years, we use a new set of vibracore and push core data (i) to contribute to a more reliable Holocene history of regional extreme-wave events and (ii) to evaluate their impact on shoreline evolution. Multi-proxy palaeoenvironmental analyses (XRF, XRD, grain size distribution, carbonate, LOI, microfossils) were carried out using nearshore sedimentary archives from the sheltered western (leeward) side of Bonaire and its small neighbour Klein Bonaire. In combination with 14C-AMS age estimates the stratigraphy reflects a long-term coastal evolution controlled by relative sea level rise, longshore sediment transport, and short-term morphodynamic impulses by extreme wave action, all three of which may have significantly influenced the development of polyhaline lagoons and the demise of mangrove populations. Extreme wave events may be categorized into major episodic incidents (c. 3.6 ka [?] BP; 3.2–3.0 ka BP; 2.0–1.8 ka BP; post-1.3 ka [?] BP), which may correspond to tsunamis and periodic events recurring on the order of decades to centuries, which we interpret as severe tropical cyclones. Extreme wave events seem to control to a certain extent the formation of coastal ridges on Bonaire and, thus, to cause abrupt shifts in the long-term morphodynamic and ecological boundary conditions of the circumlittoral inland bays.