Wave Climate and Trends for the Marine Experimental Station of Capo Tirone Based on a 70-Year-Long Hindcast Dataset

Nearshore marine systems provide multiple economic and ecological services to human communities. Several studies addressing the climate change stressors and the inappropriate use of the sea indicate a decline of coastal areas. An extensive monitoring of the most important marine sites and protected areas is crucial to design effective environmental-friendly measures to support the sustainable development of coastal regions. A 70-year-long wave climate analysis is presented to study the climatology of the area belonging to the Marine Experimental Station of Capo Tirone, Italy. The analysis is based on the global atmospheric reanalysis developed by the European Centre for Medium-Range Weather Forecasts, validated through an observed buoy dataset recorded by the Italian Sea Wave Measurement Network. No significant long-term trends have been detected. The need to set up new monitoring stations has been pointed out by means of a hydrodynamic model developed at the regional scale, evaluating the effect of the local morphology on the nearshore wave climate and highlighting the importance of surveying the marine protected area of Capo Tirone located therein.

Characteristics of the Wind and Wave Climate along the European Seas Focusing on the Main Maritime Routes

European seas have a strong economic role both in terms of transport and tourism. Providing more knowledge, regarding the mean and extreme values of the wind and sea state conditions in the areas characterized by high maritime traffic, helps to improve navigational safety. From this perspective, six zones with high maritime traffic are studied. ERA5 database, a state-of-the-art global reanalysis dataset provided by ECMWF (European Centre for Medium-Range Weather Forecasts), is used to assess the average values and the percentiles for the wind speed and the main wave parameters in the target areas considering the period 2001–2020. The main European routes and the extreme conditions along them as well as the areas characterized by high values of wind speed and high waves were also identified. A more comprehensive picture of the expected dynamics of the environmental matrix along the most significant shipping routes is useful because in this way the most dangerous areas could be avoided by ships for the safety of passengers and transported goods.

Wave Analysis for Offshore Aquaculture Projects: A Case Study for the Eastern Mediterranean Sea

The investigation of wave climate is of primary concern for the successful implementation of offshore aquaculture systems as waves can cause significant loads on them. Up until now, site selection and design (or selection) of offshore cage system structures on extended sea areas do not seem to follow any specific guidelines. This paper presents a novel methodology for the identification of favorable sites for offshore aquaculture development in an extended sea area based on two important technical factors: (i) the detailed characterization of the wave climate, and (ii) the water depth. Long-term statistics of the significant wave height, peak wave period, and wave steepness are estimated on an annual and monthly temporal scale, along with variability measures. Extreme value analysis is applied to estimate the design values and associated return periods of the significant wave height; structures should be designed based on this data, to avoid partial or total failure. The Eastern Mediterranean Sea is selected as a case study, and long-term time series of wave spectral parameters from the ERA5 dataset are utilized. Based on the obtained results, the most favorable areas for offshore aquaculture installations have been identified.

Beach and Dune Erosion: Causes and Interventions, Case Study: Kaulon Archaeological Site

The dune systems are very important from an environmental, landscape, and coastal defense point of view within coastal areas. Currently, dune systems are significantly reduced compared to a few decades ago and, in Europe alone, dune systems have decreased by 70%. During the same period, intense beach erosion processes have often been observed, and, currently, 30% of the world’s coasts are eroding. These processes have various causes, both natural and anthropogenic, and the knowledge of the causes of the erosive processes are very important for an effective planning and management of coastal areas and to correctly plan any interventions on dunes and beaches. The paper, through a case study, analyzes the beach and dune erosive processes, their causes, and the possible interventions. The case study concerns the archaeological site of Kaulon, located on a dune in the Ionian coast of Calabria (Italy). The beach near the site was affected by erosive processes and during the winter of 2013–2014, the site was damaged by two sea storms. To identify the causes of these processes, three erosive factors were analyzed. These factors are anthropogenic pressure, wave climate and sea storms, and river transport. The effects produced by these factors were assessed in terms of shoreline changes and of damage to the beach–dune system, also evaluating the effectiveness of the defense interventions. The main causes of the erosive processes were identified through the cross analysis of erosive factors and their effects. This analysis highlighted that in the second half of the last century the erosive processes are mainly correlated to anthropogenic pressure while, recently, natural factors prevail, especially sea storms. Regarding the interventions, the effects produced by two interventions carried out during the winter of 2013–2014, one built in urgency between the first and second sea storm and the other built a few years after the second sea storm were analyzed. This analysis highlighted that the latter intervention was more effective in defending the site.

Swell hindcast statistics for the Baltic Sea

The classic characterisation of swell as regular, almost monochromatic, wave trains does not necessarily accurately describe swell in water bodies shielded from the oceanic wave climate. In such enclosed areas the locally generated swell waves still contribute to processes at the air and seabed interfaces, and their presence can be quantified by partitioning wave components based on their speed relative to the wind. We present swell statistics for the semi-enclosed Baltic Sea using 20 years of swell-partitioned model data. The swell significant wave height was mostly under 2 m, and in the winter (DJF) the mean significant swell height was typically less than 0.4 m; higher swell was found in limited nearshore areas. Swell waves were typically short (under 5 s), with mean periods over 8 s being rare. In open-sea areas the average ratio of swell energy (to total energy) was mostly below 0.4 – significantly less than in the World Ocean. Certain coastal areas were swell dominated over half the time, mostly because of weak winds (U<5 m s−1) rather than high swell heights. Swell-dominated events with a swell height over 1 m typically lasted under 10 h. A cross-correlation analysis indicates that swell in the open sea is mostly generated from local wind sea when wind decays (dominant time lag roughly 15 h). Near the coast, however, the results suggest that the swell is partially detached from the local wind waves, although not necessarily from the weather system that generates them because the highest swell typically arrives with a roughly 10 h delay after the low-pressure system has already passed.

Coastal erosion in sandy beaches along a tectonically active coast: The Chile study case

Coastal erosion in 45 sandy beaches covering nearly 2000 km along the tectonically active Chilean coast is assessed during the last four decades. The historical analysis is based on the assessment of decadal changes of the shoreline position extracted from topographic surveys, aerial photographs, satellite images and survey maps using the DSAS software. Results show that 80% of the sites presented erosion rates (>−0.2 m/y), 7% beaches accreted (>0.2 m/y) while 13% remained stable. Eroded beaches include headland bay beaches, embayed and pocket beaches. A discussion on the possible causes explaining these results is conducted. While changes in offshore wave climate are spatially smooth within the region, relative mean sea level changes are highly variable and modulated by tectonic activity; the reduction of the sediment supply explains erosion rates in few cases.

Surf and Swash Dynamics on Low Tide Terrace Beaches

Low tide terrace (LLT) beaches are characterised by a moderately steep beach face and a flat shallow terrace influencing the local hydro-morphodynamics during low tide. The upper beachface slope (β) and the terrace width (Lt) are the main morphological parameters that define the shape of LTT cross-shore beach profiles. This work aims at better understanding the behaviour of β and Lt and their link with the incoming wave forcing. For this purpose, our results are based on 3.5 years times series of daily beach profiles and wave conditions surveys at two different microtidal LTT beaches with similar sediments size but different wave climate, one at Nha Trang (Vietnam) and the other one at Grand Popo (Benin). While they look similar, two contrasting behaviour were linked to two sub-types of LTT regimes: the first one is surf regulated beaches (SRB) where the swash zone is highly regulated by the surf zone wave energy dissipation on the terrace, and the second is swash regulated beaches (SwRB) acting in more reflective regime where the terrace is not active and the energy dissipation is mainly produced in the swash zone, the terrace becomes a consequences of the high dynamics in the swash zone. Finally, extending the common view of an equilibrium beach profile as a power law of the cross-shore distance, the ability of a simple parametrized cubic function model with the Dean number as unique control parameters is proposed and discussed. This simple model can be used for the understanding of LLT environments but it can not be extended to the whole beach spectrum.

Flooding of Sandy Beaches in a Changing Climate. The Case of the Balearic Islands (NW Mediterranean)

The fate of the beaches around the world has paramount importance as they are one of the main assets for touristic activities and act as a natural barrier for coastal protection in front of marine storms. Climate change could put them at risk as sea levels rise and changes in the wave characteristics may dramatically modify their shape. In this work, a new methodology has been developed to determine the flooding of sandy beaches due to changes in sea level and waves. The methodology allows a cost-effective and yet accurate estimation of the wave runup for a wide range of beach equilibrium profiles and for different seagrass coverage. This, combined with regional projections of sea level and wave evolution, has allowed a quantification of the future total water level and coastline retreat for 869 beaches across the Balearic Islands for the next decades as a function of greenhouse gases emission scenario. The most pessimistic scenario (RCP8.5) at the end of the century yields an averaged percentage of flooded area of 66% under mean conditions which increases up to 86% under extreme conditions. Moreover, 72 of the 869 beaches of the region would permanently disappear while 314 would be completely flooded during storm episodes. Under a moderate scenario of emissions (RCP4.5), 37 beaches would permanently disappear while 254 would disappear only during storm episodes. In both cases, the average permanent loss of beach surface at the end of the century would be larger than 50%, rising over 80% during storm conditions. The results obtained for the Balearic Islands can be extrapolated to the rest of the Mediterranean as the beaches in all the regions have similar characteristics and will be affected by similar changes in sea level and wave climate. These projections indicate that adaptation plans for beach areas should be put in place as soon as possible.

WEATHERING THE STORM: THE IMPLICATIONS OF WAVE EXPOSURE ON THE DISTRIBUTION, PHENOTYPE AND GROWTH OF A TEMPERATE REEF FISH

<p>Disturbance is a fundamental process that affects the structure and dynamics of populations. Wave action is an important agent of disturbance in coastal marine systems, and the frequency and severity of wave-associated disturbances is forecasted to increase with climate change. Understanding the effects of waves on coastal marine ecosystems, and the ability of organisms to adapt to wave action, is of growing importance. This is particularly true for intertidal/shallow subtidal species that are subjected to varying, sometimes intense, wave action. Most studies to-date have focused on species with limited mobility (e.g., algae and invertebrates), and have used estimates of wave dynamics that are not always relevant to the spatial scales of these organisms and their home ranges. My thesis focuses on the common triplefin, Forsterygion lapillum, an abundant benthic marine fish inhabiting shallow subtidal and intertidal rocky reefs throughout New Zealand. I develop and implement a protocol to characterise wave climates on an ecologically relevant scale. I evaluate the effects of waves on abundance, phenotype, performance, and behaviour of a reef fish. In Chapter 2, I develop and implement a protocol to characterise wave climate at an appropriate scale. The Wellington south coast is exposed to storm waves that develop in the Southern Ocean and propagate up the east coast of New Zealand. I deployed low-cost HOBO acceleration loggers at two depths within each of six locations along the Wellington south coast to record a time series of wave action at twelve sites. Data from my loggers showed substantial spatial and temporal variation in water acceleration due to interactions between waves and local topography. I used a clustering analysis to characterise my 12 sites as either ‘exposed’ or ‘sheltered’. Assignments to these exposure categories did not match with a priori predictions of exposure, suggesting that wave forces experienced by organisms in the shallow subtidal environment may be difficult to assess from surface-based observations of waves. Data were generally well-correlated with an offshore buoy at all sites, and these correlations were stronger for more exposed sites. In Chapter 3, I explored variation in fish density and phenotype through time and as a function of wave exposure. Densities peaked in summer (corresponding to seasonal recruitment) and declined over winter (consistent with increased losses during high-wave periods), and were generally greater at sheltered locations. While body condition was generally highest for fish sampled from exposed sites (consistent with a density-dependent effect on condition and/or enhancement of foraging with increasing water acceleration), other morphological characteristics did not consistently vary with wave exposure. In Chapter 4, I used otoliths to reconstruct of growth histories of individuals to further elucidate the influence of wave exposure on triplefin phenotypes. Recent growth was not influenced by wave exposure, but this was confounded by strong seasonal variation in growth rates. Lifetime growth rate also did not differ with wave exposure, and was strongly influenced by hatch date. I used mixed effects models to appropriately account for the potentially confounding effects of other features on growth, and found that daily growth rates were slightly positively correlated with site-specific daily measures of wave action. This result can potentially account for the elevated body condition of fish at exposed sites (Chapter 3), and it has important implications for fish inhabiting wave exposed coasts. In Chapter 5, I conducted a lab experiment to evaluate feeding ability in relation to simulated wave action. I used fish of a range of sizes, sampled from either a wave-sheltered or a wave-exposed site, and measured their consumption of prey in calm (low flow) conditions, disturbance (high flow) conditions, and immediately following a period of disturbance. Fish consumed fewer prey during disturbance, and more prey during calm conditions (and a similar consumption rate was observed for fish that were assayed after a period of intense wave action). While this pattern held for fish sampled from both populations, fish from wave-exposed sites consumed more prey than fish from sheltered sites, suggesting phenotypic traits (e.g., behavioural or morphological) that shape their feeding efficiency. Collectively my results suggest that organisms that inhabit wave-exposed coastlines may be intimately linked to wave climate. Waves may have direct effects on numbers (reducing densities via induced mortality) and/or indirect effects on the traits, foraging opportunities, and/or body condition of survivors. Species such as the common triplefin may exhibit plasticity in phenotypic traits that enable them to adapt to dynamic and unpredictable environments. Overall, this thesis provides insight into the ability of an intertidal/shallow subtidal species to cope with variable wave action. Such species may exhibit resilience with increasing wave action due to climate change.</p>

WEATHERING THE STORM: THE IMPLICATIONS OF WAVE EXPOSURE ON THE DISTRIBUTION, PHENOTYPE AND GROWTH OF A TEMPERATE REEF FISH

<p>Disturbance is a fundamental process that affects the structure and dynamics of populations. Wave action is an important agent of disturbance in coastal marine systems, and the frequency and severity of wave-associated disturbances is forecasted to increase with climate change. Understanding the effects of waves on coastal marine ecosystems, and the ability of organisms to adapt to wave action, is of growing importance. This is particularly true for intertidal/shallow subtidal species that are subjected to varying, sometimes intense, wave action. Most studies to-date have focused on species with limited mobility (e.g., algae and invertebrates), and have used estimates of wave dynamics that are not always relevant to the spatial scales of these organisms and their home ranges. My thesis focuses on the common triplefin, Forsterygion lapillum, an abundant benthic marine fish inhabiting shallow subtidal and intertidal rocky reefs throughout New Zealand. I develop and implement a protocol to characterise wave climates on an ecologically relevant scale. I evaluate the effects of waves on abundance, phenotype, performance, and behaviour of a reef fish. In Chapter 2, I develop and implement a protocol to characterise wave climate at an appropriate scale. The Wellington south coast is exposed to storm waves that develop in the Southern Ocean and propagate up the east coast of New Zealand. I deployed low-cost HOBO acceleration loggers at two depths within each of six locations along the Wellington south coast to record a time series of wave action at twelve sites. Data from my loggers showed substantial spatial and temporal variation in water acceleration due to interactions between waves and local topography. I used a clustering analysis to characterise my 12 sites as either ‘exposed’ or ‘sheltered’. Assignments to these exposure categories did not match with a priori predictions of exposure, suggesting that wave forces experienced by organisms in the shallow subtidal environment may be difficult to assess from surface-based observations of waves. Data were generally well-correlated with an offshore buoy at all sites, and these correlations were stronger for more exposed sites. In Chapter 3, I explored variation in fish density and phenotype through time and as a function of wave exposure. Densities peaked in summer (corresponding to seasonal recruitment) and declined over winter (consistent with increased losses during high-wave periods), and were generally greater at sheltered locations. While body condition was generally highest for fish sampled from exposed sites (consistent with a density-dependent effect on condition and/or enhancement of foraging with increasing water acceleration), other morphological characteristics did not consistently vary with wave exposure. In Chapter 4, I used otoliths to reconstruct of growth histories of individuals to further elucidate the influence of wave exposure on triplefin phenotypes. Recent growth was not influenced by wave exposure, but this was confounded by strong seasonal variation in growth rates. Lifetime growth rate also did not differ with wave exposure, and was strongly influenced by hatch date. I used mixed effects models to appropriately account for the potentially confounding effects of other features on growth, and found that daily growth rates were slightly positively correlated with site-specific daily measures of wave action. This result can potentially account for the elevated body condition of fish at exposed sites (Chapter 3), and it has important implications for fish inhabiting wave exposed coasts. In Chapter 5, I conducted a lab experiment to evaluate feeding ability in relation to simulated wave action. I used fish of a range of sizes, sampled from either a wave-sheltered or a wave-exposed site, and measured their consumption of prey in calm (low flow) conditions, disturbance (high flow) conditions, and immediately following a period of disturbance. Fish consumed fewer prey during disturbance, and more prey during calm conditions (and a similar consumption rate was observed for fish that were assayed after a period of intense wave action). While this pattern held for fish sampled from both populations, fish from wave-exposed sites consumed more prey than fish from sheltered sites, suggesting phenotypic traits (e.g., behavioural or morphological) that shape their feeding efficiency. Collectively my results suggest that organisms that inhabit wave-exposed coastlines may be intimately linked to wave climate. Waves may have direct effects on numbers (reducing densities via induced mortality) and/or indirect effects on the traits, foraging opportunities, and/or body condition of survivors. Species such as the common triplefin may exhibit plasticity in phenotypic traits that enable them to adapt to dynamic and unpredictable environments. Overall, this thesis provides insight into the ability of an intertidal/shallow subtidal species to cope with variable wave action. Such species may exhibit resilience with increasing wave action due to climate change.</p>