Hidden impacts of ocean acidification to live and dead coral framework

Cold-water corals, such as Lophelia pertusa, are key habitat-forming organisms found throughout the world's oceans to 3000 m deep. The complex three-dimensional framework made by these vulnerable marine ecosystems support high biodiversity and commercially important species. Given their importance, a key question is how both the living and the dead framework will fare under projected climate change. Here, we demonstrate that over 12 months L. pertusa can physiologically acclimate to increased CO2, showing sustained net calcification. However, their new skeletal structure changes and exhibits decreased crystallographic and molecular-scale bonding organization. Although physiological acclimatization was evident, we also demonstrate that there is a negative correlation between increasing CO2 levels and breaking strength of exposed framework (approx. 20-30% weaker after 12 months), meaning the exposed bases of reefs will be less effective 'load-bearers', and will become more susceptible to bioerosion and mechanical damage by 2100.

Effects of ocean acidification on learning in coral reef fishes

Ocean acidification has the potential to cause dramatic changes in marine ecosystems. Larval damselfish exposed to concentrations of CO2 predicted to occur in the mid- to late-century show maladaptive responses to predator cues. However, there is considerable variation both within and between species in CO2 effects, whereby some individuals are unaffected at particular CO2 concentrations while others show maladaptive responses to predator odour. Our goal was to test whether learning via chemical or visual information would be impaired by ocean acidification and ultimately, whether learning can mitigate the effects of ocean acidification by restoring the appropriate responses of prey to predators. Using two highly efficient and widespread mechanisms for predator learning, we compared the behaviour of pre-settlement damselfish Pomacentrus amboinensis that were exposed to 440 µatm CO2 (current day levels) or 850 µatm CO2, a concentration predicted to occur in the ocean before the end of this century. We found that, regardless of the method of learning, damselfish exposed to elevated CO2 failed to learn to respond appropriately to a common predator, the dottyback, Pseudochromis fuscus. To determine whether the lack of response was due to a failure in learning or rather a short-term shift in trade-offs preventing the fish from displaying overt antipredator responses, we conditioned 440 or 700 µatm-CO2 fish to learn to recognize a dottyback as a predator using injured conspecific cues, as in Experiment 1. When tested one day post-conditioning, CO2 exposed fish failed to respond to predator odour. When tested 5 days post-conditioning, CO2 exposed fish still failed to show an antipredator response to the dottyback odour, despite the fact that both control and CO2-treated fish responded to a general risk cue (injured conspecific cues). These results indicate that exposure to CO2 may alter the cognitive ability of juvenile fish and render learning ineffective.

Recuperación de energía de la salmuera

Como consecuencia del proceso de desalación, se produce el vertido al mar de un agua de rechazo hipersalino o salmuera. La salinidad de este vertido es variable, dependiendo del origen de la captación y del proceso de tratamiento. Muchos de los hábitats y biocenosis de los ecosistemas marinos se encuentran adaptados a ambientes de salinidad casi constante y son muy susceptibles a los incrementos de salinidad originados por estos vertidos. Junto con el vertido de salmuera otro de los principales inconvenientes que plantean las plantas desaladoras es el alto consumo energético, con todas las desventajas que esto supone: alto coste del agua desalada para los consumidores, contaminación del medio... El desarrollo de los métodos de vertido, herramientas de gestión de la salmuera, estudios del comportamiento de la pluma salina… ha buscado la mitigación de estos efectos sobre los ecosistemas marinos. El desarrollo en membranas de ósmosis inversa, diseño de bombas y sistemas de recuperación de energía ha permitido también la reducción del consumo energético en las plantas de desalación. Sin embargo, estos campos parecen haber encontrado un techo tecnológico difícil de rebasar en los últimos tiempos. La energía osmótica se plantea como uno de los caminos a investigar aplicado al campo de la reducción del consumo energético en desalación de agua de mar, a través del aprovechamiento energético de la salmuera. Con esta tesis se pretende cumplir principalmente con los siguientes objetivos: reducción del consumo energético en desalación, mitigar el impacto del vertido sobre el medio y ser una nueva herramienta en la gestión de la salmuera. En el presente documento se plantea el desarrollo de un nuevo proceso que utiliza el fenómeno de la ósmosis directa a través de membranas semipermeables, y busca la sinergia desalación depuración, integrando ambos, en un único proceso de tratamiento dentro del ciclo integral del agua. Para verificar los valores de producción, calidad y rendimiento del proceso, se proyecta y construye una planta piloto ubicada en la Planta Desaladora de Alicante II, escalada de tal manera que permite la realización de los ensayos con equipos comerciales de tamaño mínimo. El objetivo es que el resultado final sea extrapolable a tamaños superiores sin que el escalado afecte a la certeza y fiabilidad de las conclusiones obtenidas. La planta se proyecta de forma que el vertido de una desaladora de ósmosis inversa junto con el vertido de un terciario convencional, se pasan por una ósmosis directa y a continuación por una ósmosis inversa otra vez, ésta última con el objeto de abrir la posibilidad de incrementar la producción de agua potable. Ambas ósmosis están provistas de un sistema de pretratamiento físico-químico (para adecuar la calidad del agua de entrada a las condiciones requeridas por las membranas en ambos casos), y un sistema de limpieza química. En todos los ensayos se usa como fuente de disolución concentrada (agua salada), el rechazo de un bastidor de ósmosis inversa de una desaladora convencional de agua de mar. La fuente de agua dulce marca la distinción entre dos tipos de ensayos: ensayos con el efluente del tratamiento terciario de una depuradora convencional, con lo que se estudia el comportamiento de la membrana ante el ensuciamiento; y ensayos con agua permeada, que permiten estudiar el comportamiento ideal de la membrana. Los resultados de los ensayos con agua salobre ponen de manifiesto problemas de ensuciamiento de la membrana, el caudal de paso a través de la misma disminuye con el tiempo y este efecto se ve incrementado con el aumento de la temperatura del agua. Este fenómeno deriva en una modificación del pretratamiento de la ósmosis directa añadiendo un sistema de ultrafiltración que ha permitido que la membrana presente un comportamiento estable en el tiempo. Los ensayos con agua permeada han hecho posible estudiar el comportamiento “ideal” de la membrana y se han obtenido las condiciones óptimas de operación y a las que se debe tender, consiguiendo tasas de recuperación de energía de 1,6; lo que supone pasar de un consumo de 2,44 kWh/m3 de un tren convencional de ósmosis a 2,28 kWh/m3 al añadir un sistema de ósmosis directa. El objetivo de futuras investigaciones es llegar a tasas de recuperación de 1,9, lo que supondría alcanzar consumos inferiores a 2 kWh/m3. Con esta tesis se concluye que el proceso propuesto permite dar un paso más en la reducción del consumo energético en desalación, además de mitigar los efectos del vertido de salmuera en el medio marino puesto que se reduce tanto el caudal como la salinidad del vertido, siendo además aplicable a plantas ya existentes y planteando importantes ventajas económicas a plantas nuevas, concebidas con este diseño. As a consequence of the desalination process, a discharge of a hypersaline water or brine in the sea is produced. The salinity of these discharges varies, depending on the type of intake and the treatment process. Many of the habitats and biocenosis of marine ecosystems are adapted to an almost constant salinity environment and they are very susceptible to salinity increases caused by these discharges. Besides the brine discharge, another problem posed by desalination plants, is the high energy consumption, with all the disadvantages that this involves: high cost of desalinated water for consumers, environmental pollution ... The development of methods of disposal, brine management tools, studies of saline plume ... has sought the mitigation of these effects on marine ecosystems. The development of reverse osmosis membranes, pump design and energy recovery systems have also enabled the reduction of energy consumption in desalination plants. However, these fields seem to have reached a technological ceiling which is difficult to exceed in recent times. Osmotic power is proposed as a new way to achieve the reduction of energy consumption in seawater desalination, through the energy recovery from the brine. This thesis mainly tries to achieve the following objectives: reduction of energy consumption in desalination, mitigation of the brine discharge impact on the environment and become a new tool in the management of the brine. This paper proposes the development of a new process, that uses the phenomenon of forward osmosis through semipermeable membranes and seeks the synergy desalination-wastewater reuse, combining both into a single treatment process within the integral water cycle. To verify the production, quality and performance of the process we have created a pilot plant. This pilot plant, located in Alicante II desalination plant, has been designed and built in a scale that allows to carry out the tests with minimum size commercial equipment. The aim is that the results can be extrapolated to larger sizes, preventing that the scale affects the accuracy and reliability of the results. In the projected plant, the discharge of a reverse osmosis desalination plant and the effluent of a convencional tertiary treatment of a wastewater plant, go through a forward osmosis module, and then through a reverse osmosis, in order to open the possibility of increasing potable water production. Both osmosis systems are provided with a physicochemical pretreatment (in order to obtain the required conditions for the membranes in both cases), and a chemical cleaning system. In all tests, it is used as a source of concentrated solution (salt water), the rejection of a rack of a conventional reverse osmosis seawater desalination. The source of fresh water makes the difference between two types of tests: test with the effluent from a tertiary treatment of a conventional wastewater treatment plant (these tests study the behavior of the membrane facing the fouling) and tests with permeate, which allow us to study the ideal behavior of the membrane. The results of the tests with brackish water show fouling problems, the flow rate through the membrane decreases with the time and this effect is increased with water temperature. This phenomenon causes the need for a modification of the pretreatment of the direct osmosis module. An ultrafiltration system is added to enable the membrane to present a stable behavior . The tests with permeate have made possible the study of the ideal behavior of the membrane and we have obtained the optimum operating conditions. We have achieved energy recovery rates of 1.6, which allows to move from a consumption of 2.44 kWh/m3 in a conventional train of reverse osmosis to 2.28 kWh / m3 if it is added the direct osmosis system. The goal of future researches is to achieve recovery rates of 1.9, which would allow to reach a consumption lower than 2 kWh/m3. This thesis concludes that the proposed process allows us to take a further step in the reduction of the energy consumption in desalination. We must also add the mitigation of the brine discharge effects on the marine environment, due to the reduction of the flow and salinity of the discharge. This is also applicable to existing plants, and it suggests important economic benefits to new plants that will be built with this design.

What was natural in the coastal oceans?

Humans transformed Western Atlantic coastal marine ecosystems before modern ecological investigations began. Paleoecological, archeological, and historical reconstructions demonstrate incredible losses of large vertebrates and oysters from the entire Atlantic coast. Untold millions of large fishes, sharks, sea turtles, and manatees were removed from the Caribbean in the 17th to 19th centuries. Recent collapses of reef corals and seagrasses are due ultimately to losses of these large consumers as much as to more recent changes in climate, eutrophication, or outbreaks of disease. Overfishing in the 19th century reduced vast beds of oysters in Chesapeake Bay and other estuaries to a few percent of pristine abundances and promoted eutrophication. Mechanized harvesting of bottom fishes like cod set off a series of trophic cascades that eliminated kelp forests and then brought them back again as fishers fished their way down food webs to small invertebrates. Lastly, but most pervasively, mechanized harvesting of the entire continental shelf decimated large, long-lived fishes and destroyed three-dimensional habitats built up by sessile corals, bryozoans, and sponges. The universal pattern of losses demonstrates that no coastal ecosystem is pristine and few wild fisheries are sustainable along the entire Western Atlantic coast. Reconstructions of ecosystems lost only a century or two ago demonstrate attainable goals of establishing large and effective marine reserves if society is willing to pay the costs. Historical reconstructions provide a new scientific framework for manipulative experiments at the ecosystem scale to explore the feasibility and benefits of protection of our living coastal resources.

Global environmental impacts of agricultural expansion: The need for sustainable and efficient practices

The recent intensification of agriculture, and the prospects of future intensification, will have major detrimental impacts on the nonagricultural terrestrial and aquatic ecosystems of the world. The doubling of agricultural food production during the past 35 years was associated with a 6.87-fold increase in nitrogen fertilization, a 3.48-fold increase in phosphorus fertilization, a 1.68-fold increase in the amount of irrigated cropland, and a 1.1-fold increase in land in cultivation. Based on a simple linear extension of past trends, the anticipated next doubling of global food production would be associated with approximately 3-fold increases in nitrogen and phosphorus fertilization rates, a doubling of the irrigated land area, and an 18% increase in cropland. These projected changes would have dramatic impacts on the diversity, composition, and functioning of the remaining natural ecosystems of the world, and on their ability to provide society with a variety of essential ecosystem services. The largest impacts would be on freshwater and marine ecosystems, which would be greatly eutrophied by high rates of nitrogen and phosphorus release from agricultural fields. Aquatic nutrient eutrophication can lead to loss of biodiversity, outbreaks of nuisance species, shifts in the structure of food chains, and impairment of fisheries. Because of aerial redistribution of various forms of nitrogen, agricultural intensification also would eutrophy many natural terrestrial ecosystems and contribute to atmospheric accumulation of greenhouse gases. These detrimental environmental impacts of agriculture can be minimized only if there is much more efficient use and recycling of nitrogen and phosphorus in agroecosystems.

Assessment of Natural and Manmade Materials in US Artificial Reef Programs

Natural coral reefs are in a state of serious decline worldwide. The pressures of over fishing, recreational activities, environmental pollutants, and global warming have stressed these marine ecosystems to the breaking point. One of the oldest methods of augmenting natural reef systems is the implementation of artificial reefs. These projects are not as simple as dumping waste or scrap materials in offshore areas. Proper material selection is vital to produce a healthy artificial marine habitat that is completed on schedule and on budget. This Capstone Project will evaluate the most commonly used materials and provide a comparison of their strengths and weaknesses. This comparison provides a valuable tool for project managers as they begin the reef planning process.

Effects of climate change on fisheries : from a global to a regional perspective

Tese de doutoramento, Biologia (Biologia Marinha e Aquacultura), Universidade de Lisboa, Faculdade de Ciências, 2016

General responses of Thoracosphaera heimii grown under a range of pCO2

Ocean acidification is considered a major threat to marine ecosystems and may particularly affect calcifying organisms such as corals, foraminifera and coccolithophores. Here we investigate the impact of elevated pCO2 and lowered pH on growth and calcification in the common calcareous dinoflagellate Thoracosphaera heimii. We observe a substantial reduction in growth rate, calcification and cyst stability of T. heimii under elevated pCO2. Furthermore, transcriptomic analyses reveal CO2 sensitive regulation of many genes, particularly those being associated to inorganic carbon acquisition and calcification. Stable carbon isotope fractionation for organic carbon production increased with increasing pCO2 whereas it decreased for calcification, which suggests interdependence between both processes. We also found a strong effect of pCO2 on the stable oxygen isotopic composition of calcite, in line with earlier observations concerning another T. heimii strain. The observed changes in stable oxygen and carbon isotope composition of T. heimii cysts may provide an ideal tool for reconstructing past seawater carbonate chemistry, and ultimately past pCO2. Although the function of calcification in T. heimii remains unresolved, this trait likely plays an important role in the ecological and evolutionary success of this species. Acting on calcification as well as growth, ocean acidification may therefore impose a great threat for T. heimii.

Raw data of SCADCP (self-contained Acoustic Doppler Current Profiler) from three moorings in the Eastern Weddell Sea, 2005-2008

The success of any efforts to determine the effects of climate change on marine ecosystems depends on understanding in the first instance the natural variations, which contemporarily occur on the interannual and shorter time scales. Here we present results on the environmental controls of zooplankton distribution patterns and behaviour in the eastern Weddell Sea, Southern Ocean. Zooplankton abundance and vertical migration are derived from the mean volume backscattering strength (MVBS) and the vertical velocity measured by moored acoustic Doppler current profilers (ADCPs), which were deployed simultaneously at 64°S, 66.5°S and 69°S along the Greenwich Meridian from February, 2005, until March, 2008. While these time series span a period of full three years they resolve hourly changes. A highly persistent behavioural pattern found at all three mooring locations is the synchronous diel vertical migration (DVM) of two distinct groups of zooplankton that migrate between a deep residence depth during daytime and a shallow depth during nighttime. The DVM was closely coupled to the astronomical daylight cycles. However, while the DVM was symmetric around local noon, the annual modulation of the DVM was clearly asymmetric around winter solstice or summer solstice, respectively, at all three mooring sites. DVM at our observation sites persisted throughout winter, even at the highest latitude exposed to the polar night. Since the magnitude as well as the relative rate of change of illumination is minimal at this time, we propose that the ultimate causes of DVM separated from the light-mediated proximal cue that coordinates it. In all three years, a marked change in the migration behaviour occurred in late spring (late October/early November), when DVM ceased. The complete suspension of DVM after early November is possibly caused by the combination of two factors: (1) increased availability of food in the surface mixed layer provided by the phytoplankton spring bloom, and (2) vanishing diurnal enhancement of the threat from visually oriented predators when the illumination is quasi-continuous during the polar and subpolar summer. Zooplankton abundance in the water column, estimated as the mean MVBS in the depth range 50-300 m, was highest end of summer and lowest mid to end winter on the average annual cycle. However, zooplankton abundance varied several-fold between years and between locations. Based on satellite and in situ data of chlorophyll and sea ice as well as on hydrographic measurements, the interannual and spatial variations of zooplankton mean abundance can be explained by differences in the magnitude of the phytoplankton spring bloom, which develops during the seasonal sea ice retreat. Whereas the vernal ice melt appears necessary to stimulate the blooming of phytoplankton, it is not the determinator of the blooms magnitude, its areal extent and duration. A possible explanation for the limitation of the phytoplankton bloom in some years is top-down control. We hypothesise that the phytoplankton spring development can be curbed by grazing when the zooplankton had attained high abundance by growth during the preceding summer.

The Metula oil spill = El derramamiento petrolífero del Metula /

On cover: MESA, Marine Ecosystems Analysis Program.

Effects of Lyngbya majuscula (Cyanophycea) blooms on sediment nutrients and meiofaunal assemblages in seagrass beds in Moreton Bay, Australia

Blooms of Lyngbya majuscula have been increasingly recorded in the waters of Moreton Bay, on the south-east coast of Queensland, Australia. The influences of these blooms on sediment infauna and the implications for sediment biogeochemical processes was studied. Sediment samples were taken from Moreton Bay banks during and after the bloom season. The deposition of L. majuscula seems to be responsible for the higher total Kjedahl nitrogen (TKN) concentrations measured during the bloom period. Total organic carbon (TOC) concentrations did not change. Lyngbya majuscula blooms had a marked influence on the meiobenthos. Nematodes, copepods and polychaetes were the most abundant groups of meiofauna, and the bloom produced a decrease in the abundance and a change in the sediment depth distribution of these organisms. The distribution of nematodes, copepods and polychaetes in sediment became shallower. Further, the bloom did not affect the abundance and distribution of polychaetes as strongly as it did copepods and nematodes. The changes observed in the distribution of meiofauna in the sediment during the bloom period indicate that L. majuscula produces oxygen depletion in sediments, and that different fauna seem to be affected to different degrees.

Origin, transport and fate of organic matter in Florida Bay: A biomarker record of historical environmental changes

The Everglades are undergoing the world largest wetland restoration project with the aim of returning this system to hydrological conditions in place prior to anthropogenic modifications. Therefore, it is essential to know what these pristine conditions were. In this work, molecular marker (biomarker) distributions and carbon stable isotopic signatures in sediment samples were employed to assess historical environmental changes in Florida Bay over approximately the last 4000 years. Two biomarkers of terrestrial plants, particularly for mangroves (taraxerol and C29 n-alkane), combined with two seagrass proxies (the Paq and the C25/C 27 n-alkan-2-one ratio) revealed a sedimentary environmental shift from freshwater marshes to mangrove swamps and then to seagrass dominated marine ecosystems, likely as a result of sea-level rise in Florida Bay since the Holocene. The maximum values for the Paq and the C 25/C27 n-alkan-2-ones occurred during the 20th century, suggesting that the greatest abundance of seagrass cover is a recent rather than a historical, long-term phenomenon. The greater oscillation in frequency and amplitude for the biomarkers after 1900 potentially reflects an ecosystem under increasing anthropogenic stress. Several algal biomarkers such as C20 highly branched isoprenoids (HBIs), C 25 HBIs and dinosterol indicative of cyanobacteria, diatom and dinoflagellate organic matter inputs respectively, increased dramatically in the latter part of the 20th century and were attributed to recent anthropogenic changes in Florida Bay. ^ The highlight of this work is the development of HBIs as paleo-proxies. As biomarkers of diatoms, the C25 HBIs in the core from the central bay displayed the highest concentration at mid depth, reflecting strong historical inputs of diatom-derived sedimentary OM during that period. In fact, the depth profile of C25 HBIs coincided quite well with historical variations in diatom abundance and variations in diatom species composition in central Florida Bay based on the results of fossil diatom species analysis by microscopy. This study provides evidence that some C25 HBIs can be applied as biomarkers for certain diatom inputs in paleoenvironmental studies. The sources of C20 and C30 HBIs and their potential applicability as paleo-proxies were also investigated and their sources assessed based on their δ13C distributions. ^

Habitat use and foraging ecology of a batoid community in Shark Bay, Western Australia

Worldwide declines in populations of large elasmobranchs and the potential cascading effects on marine ecosystems have garnered considerable attention. Far less appreciated are the potential ecological impacts of changes in abundances of small to medium bodied elasmobranchs mesopredators. Crucial to elucidating the role of these elasmobranchs is an understanding of their habitat use and foraging ecology in pristine conditions. I investigated the trophic interactions and factors driving spatiotemporal variation in abundances of elasmobranch mesopredators in the relatively pristine ecosystem of Shark Bay, Australia. First, I describe the species composition and seasonal habitat use patterns of elasmobranch mesopredator on the sandflats of Shark Bay. Juvenile batoids dominated this diverse community and were extremely abundant in nearshore microhabitats during the warm season. Stomach content analysis and stable isotopic analysis revealed that there is a large degree of dietary overlap between common batoid species. Crustaceans, which tend to be found in seagrass habitats, dominated diets. Despite isotopic differences between many species, overlap in isotopic niche space was high and there was some degree of individual specialization. I then, investigated the importance of abiotic (temperature and water depth) and biotic (prey and predator abundance) factors in shaping batoid habitat use. Batoids were most abundant and tended to rest in shallow nearshore waters when temperatures were high. This pattern coincides with periods of large shark abundance suggesting batoids were seeking refuge from predators rather than selecting optimal temperatures. Finally, I used acoustic telemetry to examine batoid residency and diel use of the sandflats. Individual batoids were present on the sandflats during both the warm and cold seasons and throughout the diel cycle, suggesting lower sandflat densities during the cold season were a result of habitat shifts rather than migration out of Shark Bay. Combined, habitat use and dietary results suggest that batoids have the potential to seasonally impact sandflat dynamics through their presence, although foraging may be limited on the sandflats. Interestingly, my results suggest that elasmobranch mesopredators in pristine ecosystems probably are not regulated by food supply and their habitat use patterns and perhaps ecosystem impacts may be influenced by their predators.

Fatty acids and stable isotopes as indicators of early-life feeding and potential maternal resource dependency in the bull shark Carcharhinus leucas

The degree of reliance of newborn sharks on energy reserves from maternal resource allocation and the timescales over which these animals develop foraging skills are critical factors towards understanding the ecological role of top predators in marine ecosystems. We used muscle tissue stable carbon isotopic composition and fatty acid analysis of bull sharks Carcharhinus leucas to investigate early-life feeding ecology in conjunction with maternal resource dependency. Values of δ13C of some young-of-the-year sharks were highly enriched, reflecting inputs from the marine-based diet and foraging locations of their mothers. This group of sharks also contained high levels of the 20:3ω9 fatty acid, which accumulates during periods of essential fatty acid deficiency, suggesting inadequate or undeveloped foraging skills and possible reliance on maternal provisioning. A loss of maternal signal in δ13C values occurred at a length of approximately 100 cm, with muscle tissue δ13C values reflecting a transition from more freshwater/estuarine-based diets to marine-based diets with increasing length. Similarly, fatty acids from sharks >100 cm indicated no signs of essential fatty acid deficiency, implying adequate foraging. By combining stable carbon isotopes and fatty acids, our results provided important constraints on the timing of the loss of maternal isotopic signal and the development of foraging skills in relation to shark size and imply that molecular markers such as fatty acids are useful for the determination of maternal resource dependency.

Tropical seagrass-associated macroalgae distributions and trends relative to water quality

Tropical coastal marine ecosystems including mangroves, seagrass beds and coral reef communities are undergoing intense degradation in response to natural and human disturbances, therefore, understanding the causes and mechanisms present challenges for scientist and managers. In order to protect our marine resources, determining the effects of nutrient loads on these coastal systems has become a key management goal. Data from monitoring programs were used to detect trends of macroalgae abundances and develop correlations with nutrient availability, as well as forecast potential responses of the communities monitored. Using eight years of data (1996–2003) from complementary but independent monitoring programs in seagrass beds and water quality of the Florida Keys National Marine Sanctuary (FKNMS), we: (1) described the distribution and abundance of macroalgae groups; (2) analyzed the status and spatiotemporal trends of macroalgae groups; and (3) explored the connection between water quality and the macroalgae distribution in the FKNMS. In the seagrass beds of the FKNMS calcareous green algae were the dominant macroalgae group followed by the red group; brown and calcareous red algae were present but in lower abundance. Spatiotemporal patterns of the macroalgae groups were analyzed with a non-linear regression model of the abundance data. For the period of record, all macroalgae groups increased in abundance (Abi) at most sites, with calcareous green algae increasing the most. Calcareous green algae and red algae exhibited seasonal pattern with peak abundances (Φi) mainly in summer for calcareous green and mainly in winter for red. Macroalgae Abi and long-term trend (mi) were correlated in a distinctive way with water quality parameters. Both the Abi and mi of calcareous green algae had positive correlations with NO3−, NO2−, total nitrogen (TN) and total organic carbon (TOC). Red algae Abi had a positive correlation with NO2−, TN, total phosphorus and TOC, and the mi in red algae was positively correlated with N:P. In contrast brown and calcareous red algae Abi had negative correlations with N:P. These results suggest that calcareous green algae and red algae are responding mainly to increases in N availability, a process that is happening in inshore sites. A combination of spatially variable factors such as local current patterns, nutrient sources, and habitat characteristics result in a complex array of the macroalgae community in the seagrass beds of the FKNMS.