Tidal Height Research Articles

The lunar nodal cycle controls mangrove canopy cover on the Australian continent.

Long-phase (interannual) tidal cycles have been shown to influence coastal flooding and sedimentation, but their role in shaping the extent and condition of tidal wetlands has received little attention. Here, we show that the 18.61-year lunar nodal cycle, popularly termed the “lunar wobble,” is a dominant control over the expansion and contraction of mangrove canopy cover over much of the Australian continent. Furthermore, the contrasting phasing of the 18.61-year lunar nodal cycle between diurnal and semidiurnal tidal settings has mediated the severity of drought impacts in northern bioregions. Long-phase tidal cycles regulate maximum tide heights, are an important control over mangrove canopy cover, and may influence mangrove ecosystem services including forest productivity and carbon sequestration at regional scales.

A Numerical Study of Long-Return Period Near-Bottom Ocean Currents in Lower Cook Inlet, Alaska

Lower Cook Inlet (LCI) is an important waterway with very large tides and high marine productivity. Oceanographic forcing in LCI is complex due to a combination of tides, seasonal winds, and large freshwater discharges, as well as inflow from the Alaska Coastal Current. From an analysis of historical current meter data sets, deeper ocean currents of LCI were found to have large differences resulting from the dominance of large tides in the northeast portion of LCI while subtidal contributions to the deeper currents are more important relative to the reduced tidal currents in central and western parts of LCI. To compute the largest values of the near-bottom currents of LCI, a 3D hydrodynamical model was developed over a large model domain extending over the full 300 km length of Cook Inlet as well as a large portion of the adjoining Alaska continental shelf region. At the open model boundaries, nine major tidal height constituents were specified based on National Oceanic and Atmospheric Administration (NOAA) tidal gauge data. The model was forced by the spatially varying winds and freshwater discharges for the six gauged rivers in Cook Inlet. The model was verified using available current meter data in the study area. Model runs were carried out for 21 case studies to derive the near-bottom currents for return periods of 1, 10, and 100 years. Within LCI, the extremal values for near bottom currents arise from quite different forcing regimes. Tidal currents are completely dominant in the northeast portion of LCI while for central and western portions, remote wind forcing over the Alaskan continental shelf current, which generates the Alaska Coastal Current, becomes more important.

Abiotic factors associated with microplastic pollution in surface water of a tropical estuary

The aquatic environment has suffered anthropic impacts through inadequate dumping from domestic, agricultural and industrial sources. Such waste products become fragmented into microplastics (MPs) which accumulate in these ecosystems and cause impact. This study offers the first evaluation of contamination of the surface water by MPs in the Paraíba River estuary, Paraíba State, northeast Brazil. Monthly surface water samples were performed with a phytoplankton net from March 2019 to February 2020, between Restinga Island and the Cabedelo Harbor, downstream of the estuary. About the abiotic factors tested, tide height and precipitation were inversely proportional to MPs abundance at the water surface. While water transparency, wind speed and direction and volume of filtered water did not affect it significantly. A total of 443 MPs were obtained in 1116.26 m3 of filtered water, with a mean abundance of 1.96 ± 1.44 MP/m3, ranging from 0.33 (September) to 4.76 (January). The results reveal an important incidence of MPs pollution downstream in this system. The predominance of MPs fibers (51%) and fragments (48%) result from the slow, natural breakdown of solid waste, confirming the lack of the proper discarding to trash in the João Pessoa metropolitan region. These findings underscore the need for the implementation of simple mitigating measures, such as basic sanitation to reduce local pollution as well as effective routine assessments from the anthropic impact and from water quality control measures in this and many other Brazilian estuaries.

Assessment of the environmental drivers of European glass eel (Anguilla anguilla) recruitment in transitional waters

The European eel (Anguilla anguilla) has undergone an unprecedented population decline since the 1980s, with current recruitment levels fluctuating from 3 to 15% of historical levels for the last 20 years. Monitoring of glass eels and elvers as 0 + recruitment is an essential step in helping to understand the trend in recruitment and to better quantify the current recruitment time series. Two locations within the Shannon estuary on the west coast of Ireland were monitored for glass eel recruitment from January to April in 2017 and 2018. This study used a generalised linear mixed model to examine a range of environmental variables impacting on glass eel abundance in transitional waters. Results found that water temperature and moon phase were the most important variables. Tidal height and cloud cover also influenced the abundance of glass eels but to a lesser extent. This study found that focussing survey efforts on nights around the full moon when water temperatures exceed 5℃ will allow a catch which is representative of the population in an estuary. Glass eel monitoring needs a long-term sampling plan in order to account for annual fluctuations apparent in glass eel recruitment.

Accumulative responses of soft clayey seabed: A case study from the Eastern Coast of China

Existing seawalls along the eastern coast of China are increasingly becoming the focus of upgrade operations. Concerns arise regarding the settling and stability of seawalls built on soft clayey seabed during upgrade operations. Pore water pressure (PWP) and horizontal displacement accumulations induced by combined tide and wave loadings are observed in in-situ measurements of the clayey seabed underneath the seawall. The measurement results show clear correlations between the oscillations of excess PWP and variations in the tidal height. To reproduce the quasi-static interaction behaviors of the gravity-type seawall and clayey seabed under combined cyclic loadings from waves and currents, a finite element model has been built after incorporating a stiffness degradation law that is evaluated from laboratory triaxial tests on the seabed soil. Demonstrably, with a suitable stiffness degradation law for the seabed soil, the accumulative behaviors can be reasonably reproduced using finite-element modeling.

Mission Planning for Low Altitude Aerial Drones during Water Sampling

Mission planning for small uncrewed aerial systems (sUAS) as a platform for remote sensors goes beyond the traditional issues of selecting a sensor, flying altitude/speed, spatial resolution, and the date/time of operation. Unlike purchasing or contracting imagery collections from traditional satellite or manned airborne systems, the sUAS operator must carefully select launching, landing, and flight paths that meet both the needs of the remote sensing collection and the regulatory requirements of federal, state, and local regulations. Mission planning for aerial drones must consider temporal and geographic changes in the environment, such as local weather conditions or changing tidal height. One key aspect of aerial drone missions is the visibility of the aircraft and communication with the aircraft. In this research, a visibility model for low-altitude aerial drone operations was designed using a GIS-based framework supported by high spatial resolution LiDAR data. In the example study, the geographic positions of the visibility of an aerial drone used for water sampling at low altitudes (e.g., 2 m above ground level) were modeled at different levels of tidal height. Using geospatial data for a test-case environment at the Winyah Bay estuarine environment in South Carolina, we demonstrate the utility, challenges, and solutions for determining the visibility of a very low-altitude aerial drone used in water sampling.

Improved BSO for ship path planning with grounding alert using interpolated Delaunay triangulation

ABSTRACT An improved depth-contour points generation algorithm under navigation safety constraints based on possible shallowest sounding and interpolation is proposed. An improved brain storm optimisation (BSO) for ship path planning with grounding alert using interpolated Delaunay triangulation is designed. The initial clustering centre selection method is improved to overcome the sensitivity of the initial value generated by the k-means algorithm. The clustering algorithm of the random walking centroid is used to improve the efficiency, stability, randomness, and diversity of the iterative process and prevents convergence to the local optimal solution. The tide height with grounding alert is considered in path planning to ensure that real-time water depth is deeper than the safe water depth threshold. The curve interpolation method is used for points protruding into shallow water, while the linear interpolation method is used for points protruding into deep water.

DETERMINACIÓN DEL CAUDAL VOLUMÉTRICO A LO LARGO DE UN ESTUARIO CON ONDA DE MAREA ESTACIONARIA

The hydrodynamic behaviour of the micro tidal and 13.9-km-long Quequén Grande River estuary (Buenos Aires, Argentina), in which the tide behaves as a standing wave, is studied analytically and numerically. Results provided by the SisBaHiA program are validated with the measurements performed with two acoustic Doppler current profilers in stations located at 1.4, 2.9, 7.5 and 11.3 km from the estuary mouth. The numerical model reproduces the differences between the measured water column height and the equilibrium height in each station. In particular, the numerical values of the flow and tidal height are analyzed during a spring tide cycle by considering nine times corresponding to the maximum, minimum, and close to the equilibrium levels. The time variations in the free surface height and flow along the estuary are explained successfully by an analytical model based on the Saint Venant one-dimensional equations as a function of the river discharge and the tidal height in the estuary mouth and the bed and friction slopes.

Harsh intertidal environment enhances metabolism and immunity in oyster (Crassostrea gigas) spat

The Pacific oyster Crassostrea gigas is established in the marine intertidal zone, experiencing rapid and highly dynamic environmental changes throughout the tidal cycle. Depending on the bathymetry, oysters face oxygen deprivation, lack of nutrients, and high changes in temperature during alternation of the cycles of emersion/immersion. Here we showed that intertidal oysters at a bathymetry level of 3 and 5 m delayed by ten days the onset of mortality associated with Pacific Oyster Mortality Syndrome (POMS) as compared to subtidal oysters. Intertidal oysters presented a lower growth but similar energetic reserves to subtidal oysters but induced proteomic changes indicative of a boost in metabolism, inflammation, and innate immunity that may have improved their resistance during infection with the Ostreid herpes virus. Our work highlights that intertidal harsh environmental conditions modify host-pathogen interaction and improve oyster health. This study opens new perspectives on oyster farming for mitigation strategies based on tidal height.

Optimization of safe navigability conditions in shallow inland waters: The Routinav app

Safe navigation in inland waters subjected to tide requires dedicated forecasts of meteorological and oceanographic variables, such as local tidal height, currents, wind and atmospheric pressure. Indeed, it is more difficult to navigate inland shallow waters subjected to intense morphologic dynamics, and therefore characterized by the non-linearity of the tidal height propagation throughout the channels, traduced by important changes in tidal amplitude and phase, especially when no navigation aids are installed. In this context, this work objective is a mobile application (Routinav) development that allows simulating the navigability conditions in inland shallow waters. Firstly, a monitoring system was installed on volunteer boats and validated in Ria de Aveiro, showing high accuracy in depth and position acquisition. Secondly, was designed and applied an algorithm allowing the identification of navigable and non-navigable route segments, according to the updated depth and forecasted tidal height by the hydrodynamic model. Based on this algorithm, was created an agile prototype used to build up the Routinav mobile application for iOS (iPhone OS) and Android operating systems.

Pemodelan Banjir Rob Wilayah Jakarta Utara Menggunakan Sistem Informasi Geografis

Rising sea levels originating from high tides and inundating land are known as tidal flooding. The cases of tidal floods are increasing day by day, especially in areas directly adjacent to the high seas. One of the areas that are prone to tidal flooding is North Jakarta. This study aims to determine the areas affected by the tidal flood and the extent of the area affected by the tidal flood in the Jakarta City area. This research can be used to take preventive action for residents to face the tidal flood disaster. The tidal flood height modeling was obtained based on the value of Mean Sea Level (MSL), Higher High Water Level (HHWL), and the trend of global rising tides. The result of this study is a map of areas affected by tidal flooding, where the lowest is at an altitude of 0.4 m in Penjaringan and Cilincing. At the height of this tidal flood, the impact was approximately 54 hectares of residential areas, 59 hectares of buildings, and 146 hectares of agricultural activities. The highest area affected by the tidal flood is at an altitude of 1.96 m which inundates the coastal District of Penjaringan, Cilincing, Pademangan, and Tanjung Priok Port. The height of the highest tidal flood impacts 983 ha of residential areas, 493 ha of buildings, and 830 ha of the agricultural sector were inundated. At the height of the tidal flood, which is almost 2 m high, it is necessary to carry out careful disaster mitigation efforts for the local government.

An Improved Submerged Mangrove Recognition Index-Based Method for Mapping Mangrove Forests by Removing the Disturbance of Tidal Dynamics and S. alterniflora

Currently, it is a great challenge for remote sensing technology to accurately map mangrove forests owing to periodic inundation. A submerged mangrove recognition index (SMRI) using two high- and low-tide images was recently proposed to remove the influence of tides and identify mangrove forests. However, when the tidal height of the selected low-tide image is not at the lowest tidal level, the corresponding SMRI does not function well, which results in mangrove forests below the low tidal height being undetected. Furthermore, Spartina alterniflora Loisel (S. alterniflora) was introduced to China in 1979 and rapidly spread to become the most serious invasive plant along the Chinese coastline. The current SMRI has failed to distinguish S. alterniflora from submerged mangrove forests because of their similar spectral signatures. In this study, an SMRI-based mangrove forest mapping method was developed using the time series of Sentinel-2 images to mitigate the two aforementioned issues. In the proposed method, quantile synthesis was applied to the time series of Sentinel-2 images to generate a lowest-tide synthetic image for creating SMRI to identify submerged mangrove forests. Unsubmerged mangrove forests were classified using a support vector machine, and a preliminary mangrove forest map was created by merging them. In addition, S. alterniflora was distinguished from the mangrove forests by analyzing their phenological differences. Finally, mangrove forest mapping was performed by masking S. alterniflora. The proposed method was applied to the entire coastline of the Guangxi Province, China. The results showed that it can reliably and accurately identify submerged mangrove forests derived from SMRI by synthesizing low- and high-tide images using quantile synthesis, and the differentiation of S. alterniflora using phenological differences results in more accurate mangrove mapping. This work helps to improve the accuracy of mangrove forest mapping using SMRI and its feasibility for coastal wetland monitoring. It also provides data for sustainable management, ecological protection, and restoration of vegetation in coastal zones.

The Potential for Great Barrier Reef Regional Climate Regulation via Dimethylsulfide Atmospheric Oxidation Products

Research related to the potential for coral reef-derived dimethylsulfide (DMS) oxidation products to regulate the regional climate of the Great Barrier Reef (GBR) according to the CLAW hypothesis is summarized in this mini review. The GBR has been indicated as a region of high DMS production where atmospheric emissions may be increased when corals are subject to environmental stresses associated with low tide. During low wind speeds over aerially exposed coral reefs, plumes of atmospheric DMS and new sulfate-containing nano-particle production under photo-oxidative conditions have been detected on the GBR. Hygroscopic growth of these particles in combination with coagulation and condensation processes could potentially provide a coral-mediated mechanism of new aerosol for seeding low-level stratocumulus clouds. Fine mode aerosol optical depth over GBR coral reefs has been correlated with low wind speeds and a coral stress metric formulated as a function of irradiance, water clarity, and tide height. This correlation has been proposed as a possible mechanism by which the GBR might alter the optical properties of the overlying atmosphere to attenuate local insolation leading to regional climate regulation. However, recent regional-scale aerosol-climate modeling indicates that the potential for GBR regional climate regulationviaDMS atmospheric oxidation products is weak under current anthropogenic conditions which have instigated mass coral bleaching events along the entire length of the GBR between 1998 and 2022. This increased bleaching indicates that DMS oxidation products are insufficient to regulate the regional climate of the GBR according to the CLAW hypothesis under current global warming conditions.

Remote Sensing of Surface and Subsurface Soil Organic Carbon in Tidal Wetlands: A Review and Ideas for Future Research

Tidal wetlands, widely considered the most extensive reservoir of soil organic carbon (SOC), can benefit from remote sensing studies enabling spatiotemporal estimation and mapping of SOC stock. We found that a majority of the remote-sensing-based SOC mapping efforts have been focused on upland ecosystems, not on tidal wetlands. We present a comprehensive review detailing the types of remote sensing models and methods used, standard input variables, results, and limitations for the handful of studies on tidal wetland SOC. Based on that synthesis, we pose several unexplored research questions and methods that are critical for moving tidal wetland SOC science forward. Among these, the applicability of machine learning and deep learning models for predicting surface SOC and the modeling requirements for SOC in subsurface soils (soils without a remote sensing signal, i.e., a soil depth greater than 5 cm) are the most important. We did not find any remote sensing study aimed at modeling subsurface SOC in tidal wetlands. Since tidal wetlands store a significant amount of SOC at greater depths, we hypothesized that surface SOC could be an important covariable along with other biophysical and climate variables for predicting subsurface SOC. Preliminary results using field data from tidal wetlands in the southeastern United States and machine learning model output from mangrove ecosystems in India revealed a strong nonlinear but significant relationship (r2 = 0.68 and 0.20, respectively, p < 2.2 × 10−16 for both) between surface and subsurface SOC at different depths. We investigated the applicability of the Soil Survey Geographic Database (SSURGO) for tidal wetlands by comparing the data with SOC data from the Smithsonian’s Coastal Blue Carbon Network collected during the same decade and found that the SSURGO data consistently over-reported SOC stock in tidal wetlands. We concluded that a novel machine learning framework that utilizes remote sensing data and derived products, the standard covariables reported in the limited literature, and more importantly, other new and potentially informative covariables specific to tidal wetlands such as tidal inundation frequency and height, vegetation species, and soil algal biomass could improve remote-sensing-based tidal wetland SOC studies.

Distribution of 222Rn in Seawater Intrusion Area and Its Implications on Tracing Submarine Groundwater Discharge on the Upper Gulf of Thailand

Abstract Radon (222Rn) has been widely employed as a tracer for estimating submarine groundwater discharge (SGD). However, the uncertainty of the SGD estimation remains significant, due to the spatial variability of radon in groundwater. In this study, we analyzed the hydrochemical proprieties of seawater and coastal groundwater in the Upper Gulf of Thailand and discussed the distribution characteristics of 222Rn in aquifers in terms of aquifer lithology, groundwater system recharge conditions, and water retention time. The results suggested that the residence time of groundwater and the process of groundwater salinization have the greatest impact on the distribution of 222Rn activity. A 222Rn mass balance model, synthesizing the distribution characteristics of 222Rn in groundwater and tidal influences on SGD, was built to estimate the submarine groundwater discharge in the Upper Gulf of Thailand. The result showed that the SGD flux of the Upper Gulf of Thailand was 0.0203 m/d. Moreover, there is a positive correlation between tidal height and the activity of 222Rn in groundwater. The SGD observed during the low tide was about 1.25 times higher than that observed during the high tide. This may influence the marine geochemical cycles of elements and their impact on marine ecosystems.

Topography and morphodynamic study of intertidal mudflats along the eastern coast of the Gulf of Khambhat, India using remote sensing techniques

The intertidal mudflats that are exposed subaerially between the high and low tides have a complex morphology comprising ebb and flood tidal deltas, spits, shoals, and tidal sandbanks intervened with a network of meandering and branching tidal channels and inlets. The intertidal zones are highly transient and understanding their morphodynamics is critical to the ecology and economy of the region. Monitoring intertidal mudflat dynamics is imperative for sustainable development activities along coastal regions. The topography of intertidal mudflat is estimated for the eastern coast of the Gulf of Khambhat (north-western coast of India) using the waterline detection method from a series of satellite images. We have used Modified Normalized Difference Water Index and image threshold techniques to delineate waterlines from satellite images of high to low tidal conditions at different tidal heights. The waterlines are considered as elevation contours corresponding to tidal height during satellite observation, and a series of elevation contours delineated from satellite images of various tidal heights are then used to calculate the mudflat topography. The estimated topography is validated with the Differential Global Positioning System (DGPS), the Sound and navigation ranging (Sonar), and ICESat-2 ATL03 dataset observations, which results in R2 values of 0.97, 0.89, and 0.9, respectively, as well as RMSE values of 0.39 m, 0.33 m, and 0.49 m, respectively. The mudflat dynamics are studied by comparing the topographical changes estimated between the satellite images of 1998-99 and 2019. The major morphological changes are the landward shift of the low waterline, lateral migration of tidal bars, narrowing of the river mouth, as well as anthropogenic influences such as mudflat reclamation and impedance of long-shore sediment transport. The region with deposition of sediment above Mean Sea Level (MSL) has flattened the slope, making the mudflat stable and promoting mangroves expansion, while erosion has steepened the mudflats with loss of mangrove cover. These mudflats exhibit highly complex morphological changes mainly induced by sediment transport, two-way tidal currents, and fluvial fluxes. The estimated topography shall find its application in modeling coastal processes, identifying vulnerable coastal stretches, and site suitability for mangrove plantations.

THE DESIGN MODEL OF INTENSIVE VANAME SHRIMP PONDS FOR ECO-GREEN AQUACULTURE DEVELOPMENT IN THE AREA OF PROBOLINGGO, EAST JAVA, INDONESIA

Probolinggo, East Java, Indonesia, is an area with a high potential for shrimp aquaculture because these areas meet the criteria for candidate vaname shrimp aquaculture. Probolinggo in tropical regions with stable climate dan sea waves that have the potential for vaname shrimp aquaculture. The analysis required the following data: tidal data, topographic maps, network layouts, and water quality data for shrimp. This research was conducted by using the facilities at the brackish water and Marine Fisheries Laboratory of Probolinggo; an eco-green aquaculture circulation system was modeled and assessed using shrimp pond. First, the survey was located in Probolinggo City area, with coordinates 7° 44? 30.03? S and 113° 13? 58.68?. The methods used hydrological analysis: Water needs analysis for aquaculture irrigation based on the rules given by the Food and Agriculture Organization and water circulation analysis (Feedpedia, 2016). Material strength analysis of the embankments of the model pools: The comparison of area ratio toward embankment type dimension, design of dike and ponds, water filling discharge of brackish-water pond, and stages for ponds model design development. The results of the research suggested that dike should be planned to be as high as 1.5 m at the highest tide. The results of observations and tables of tidal recordings that had been verified then became the primary benchmark for planning the shrimp pond bottom. Based on the results of the analysis, it was found that the tidal height in the study location areas ranged from 2.5 to 3 m. A total of 80% of the area was used for production ponds.

Biophysical Controls of Ecosystem‐Scale Methane Fluxes From a Subtropical Estuarine Mangrove: Multiscale, Nonlinearity, Asynchrony and Causality

AbstractMangroves are complex ecosystems subject to periodic and irregular changes in meteorology, tides, water quality and biological factors. Methane dynamics in mangroves and their dependence on biogeochemical controls across scales are poorly characterized using traditional parametric statistics. We measured the ecosystem‐scale methane flux (FCH4) using an eddy covariance system in a subtropical estuarine mangrove for two years. A combination of nonparametric statistical approaches, including singular spectrum analysis and information theory, was used to isolate multiscale FCH4 variations and explore their variability and dominant controls at different time scales. FCH4 exhibited the largest variability at the diel scale (57%), followed by seasonal (25%) and multiday (18%) scales. Mutual information metrics suggested that variation in FCH4 was dominantly coupled to plant activities through synchronous processes at the diel scale. Moreover, fluctuations in atmospheric turbulence and soil temperature dominated multiday variation in FCH4 through asynchronous processes. Seasonally, soil temperature and water salinity were dominant variables leading to changes in FCH4 with a time lag of 12 and 17 days, respectively. Weak links between FCH4 and tidal heights were found across all the studied time scales. Transfer entropy metrics indicated that a super typhoon event substantially weakened causal links between biophysical variables and FCH4 by causing severe defoliation and disturbing the soil microbial community. The typhoon also temporarily decoupled the causal link between FCH4 and temperature. These findings call for the inclusion of the properties of scale emergence, nonlinearity, asynchrony and causality for comprehensively understanding and accurately predicting the interactions between mangrove FCH4 and its biophysical controls.

Monitoring 23-year of shoreline changes of the Zengwun Estuary in Southern Taiwan using time-series Landsat data and edge detection techniques

More than 80% of sandy beaches in Taiwan have been experiencing a severe recession, although the sediment discharge of rivers in Taiwan is significantly higher than the world average producing almost 2% of global fluvial sediment discharge. This contradiction is primarily due to the widespread constructions of reservoirs and intensive anthropogenic activities in coastal regions. In addition, coasts are particularly vulnerable to hazards due to climate change, such as sea-level rise, as they are located at the transition zone of terrestrial and marine environments. Along with the fact that Taiwan is an island and is one of the most climate-vulnerable regions globally, coastal management and sustainability are nationally critical topics, especially considering the ongoing reformation and legislation of Taiwan's coastal conservation laws.As stated in the Sustainable Development Goals (SDGs) goal 14, accurate and continuous shoreline positions information is essential for coastal conservation. However, by reviewing previous global studies and projects commissioned by the Taiwanese government aiming at monitoring shoreline changes, they usually exhibit several limitations, such as limited band selections or conservative band ratio-derived water indices, relying on either manual digitization or simple thresholding methods, focusing on either artificial or smoothly shaped coasts, and using images acquired at considerably different tidal height levels.Therefore, in the present study, a subpixel shoreline extraction approach based on a sustainable cross-generation dataset and a robust edge detection algorithm is proposed. This approach is exemplified by the Zengwun River Estuary located in southwestern Taiwan—Taiwan's most critical coastal preservation region. By quantitatively analyzing the resultant time-series shoreline positions from 1999 to 2021, several hotspots of shoreline recession have been identified: an extreme erosional rate up to −69.4 m year−1 is revealed in the northern sand bank; while the offshore sand bar demonstrates an overall landward retreat rate of −35.4 ± 1.24 m year−1.

Frequency of Temperature Fluctuations Subtly Impacts the Life Histories of a Tropical Snail.

AbstractMost organisms are faced with daily cyclic changes in a suite of environmental conditions, including temperature. In shallow marine waters, populations of the same species may experience either intertidal or subtidal conditions, such that some individuals experience extreme daily fluctuations as the tide ebbs and flows, while others only a few meters away experience less pronounced or less frequent fluctuations or almost constant thermal conditions. This study used a fully factorial combination of three thermal treatments and two diet treatments to test the hypotheses that (1) individuals experiencing fluctuating temperatures perform more poorly than those experiencing the same mean temperature under constant conditions and that (2) the negative impact of fluctuating temperatures is greater under food-limiting conditions. Five life-history components of the slipper snail Crepidula cf. marginalis were used as response variables. We found that temperature fluctuations impacted size at hatching and time to hatching, as well as growth rate, to some extent. Diet treatments impacted growth rates, clutch sizes, time to first brood, and time to hatching. There were no statistically significant interactions between the two factors. These results show that fluctuations between two temperatures that are typically experienced by these animals in the field can significantly affect fitness-related characters and, therefore, suggest the tidal height at which larvae settle can significantly impact individual fitness. This is one of the first studies to demonstrate that differences in the frequency of fluctuations, in the absence of differences in the magnitude or the mean, can have significant impacts on invertebrate life histories.