Seagrass Management Research Articles

SEAGRASS POPULATION CONNECTIVITY IN THE SOUTH CHINA SEA

Seagrass plays important ecological roles and ecosystem services, yet degrading alarmingly in the South China Sea (SCS), one of the largest marginal seas of the Western Pacific. As connectivity is a vital component in population persistence, understanding of connectivity is of importance for effective seagrass conservation management. In the South China Sea, our understanding of connectivity is mainly based on studies in fishes and invertebrates. Connectivity in seagrass populations, on the other hand, is still poorly investigated. In this review, I predict that genetically structured population of seagrass is likely to occur in the SCS. Future research on seagrass connectivity should include (i) investigation on the pattern of connectivity at a local and broader-regional scale, and (ii) investigation on processes involved in the seagrass connectivity. These investigations are aimed to improve our knowledge of seagrass connectivity and to contribute in providing a solid framework for seagrass restoration/transplantation and spatial planning of seagrass management.

Climate Change Impacts on Seagrass Meadows and Macroalgal Forests: An Integrative Perspective on Acclimation and Adaptation Potential

Marine macrophytes are the foundation of algal forests and seagrass meadows¬–some of the most productive and diverse coastal marine ecosystems on the planet. These ecosystems provide nursery grounds and food for fish and invertebrates, coastline protection from erosion, carbon sequestration, and nutrient fixation. For marine macrophytes, temperature is generally the most important range limiting factor, and ocean warming is considered the most severe threat among global climate change factors. ocean warming induced losses of dominant macrophytes along their equatorial range edges, as well as range extensions into polar regions, are predicted and already documented. While adaptive evolution based on genetic change is considered too slow to keep pace with the increasing rate of anthropogenic environmental changes, rapid adaptation may come about through a set of non-genetic mechanisms involving the functional composition of the associated microbiome, as well as epigenetic modification of the genome and its regulatory effect on gene expression and the activity of transposable elements. While research in terrestrial plants demonstrates that the integration of non-genetic mechanisms provide a more holistic picture of a species' evolutionary potential, research in marine systems is lagging behind. Here, we aim to review the potential of marine macrophytes to acclimatize and adapt to major climate change effects via intraspecific variation at the genetic, epigenetic, and microbiome levels. All three levels create phenotypic variation that may either enhance fitness within individuals (plasticity) or be subject to selection and ultimately, adaptation. We review three of the most important phenotypic variations in a climate change context, including physiological variation, variation in propagation success, and in herbivore resistance. Integrating different levels of plasticity, and adaptability into ecological models will allow to obtain a more holistic understanding of trait variation and a realistic assessment of the future performance and distribution of marine macrophytes. Such multi-disciplinary approach that integrates various levels of intraspecific variation, and their effect on phenotypic and physiological variation, is of crucial importance for the effective management and conservation of seagrasses and macroalgae under climate change.

Macro-grazer herbivory regulates seagrass response to pulse and press nutrient loading

Coastal ecosystems are exposed to multiple stressors. Predicting their outcomes is complicated by variations in their temporal regimes. Here, by means of a 16-month experiment, we investigated tolerance and resistance traits of Posidonia oceanica to herbivore damage under different regimes of nutrient loading. Chronic and pulse nutrient supply were combined with simulated fish herbivory, treated as a pulse stressor. At ambient nutrient levels, P. oceanica could cope with severe herbivory, likely through an increase in photosynthetic activity. Elevated nutrient levels, regardless of the temporal regime, negatively affected plant growth and increased leaf nutritional quality. This ultimately resulted in a reduction of plant biomass that was particularly severe under chronic fertilization. Our results suggest that both chronic and pulse nutrient loadings increase plant palatability to macro-grazers. Strategies for seagrass management should not be exclusively applied in areas exposed to chronic fertilization since even short-term nutrient pulses could alter seagrass meadows.

Pressures and Status of Seagrass Ecosystem in the Coastal Areas of North Bintan, Indonesia

This study investigates the status and anthropogenic pressures on seagrass ecosystem. Urbanization and tourism in the coastal areas of Bintan, Indonesia were increasing in the recent years. They have become new pressures to intertidal ecosystem and habitats, particularly seagrass ecosystem. Seagrass meadows are the important ecosystem and habitats in Bintan region. They provide a wide range of ecosystem services, including for small-scale fisheries and have being Dugongs (Dugong dugon) habitats for food. Currently, the sea grass status is less healthy or damaged with 11 species. The anthropogenic disturbance processes have affected the spatial distribution, percent coverage, biodiversity, and community structure of sea grass. Moreover, several species are hard to find. Directly, sea grass meadows are impacted by introduced coastal development (i.e. settlement area, tourism accommodation, port, etc.), land-based pollution, reclamation, boating traffic, dredging activities and tourism activities. Sea grass conservation area and marine spatial planning based on the land- and seascape connectivity is important for conservation efforts and sustainable management of sea grass.

Early steps for successful management in small-scale fisheries: An analysis of fishers', managers' and scientists' opinions preceding implementation

This study analyzes fishers', managers' and scientists' opinions on management measures to facilitate the initiation of management processes towards more sustainable small-scale seagrass fisheries in Zanzibar, Tanzania. The results show that most fishers and managers agreed on the need to include seagrasses specifically in future management. There was further agreement on dragnets being the most destructive gears, and the use of dragnets being a major threat to local seagrass ecosystems. Gear restrictions excluding illegal dragnets were the favored management measure among fishers. Differences between fishers and managers were found concerning seaweed farming, eutrophication and erosion being potential threats to seagrass meadows. A majority of the interviewed fishers were willing to participate in monitoring and controls, and most fishers thought that they themselves and their communities would benefit the most from establishing seagrass management. Co-managed gear restrictions and the inclusion of different key actos in the management process including enforcement are promising starting points for management implementation.

Land use is a better predictor of tropical seagrass condition than marine protection

Effective coastal conservation requires a better understanding of how human activities on land may directly and indirectly affect adjacent marine communities. However, the relationship between terrestrial and marine systems has rarely been considered in terrestrial and marine reserve design. Seagrasses are affected by land-based activities due to their proximity to terrestrial systems and sensitivity to fluxes of terrestrially-derived organic and inorganic material. Our study examines how land use patterns adjacent to seagrass meadows influence the ecological integrity of seagrass using a suite of seagrass condition metrics on a landscape level across the Philippine archipelago. Using canonical correlation analysis, we measured the association between environmental variables (land use and seagrass abiotic conditions) with biotic variables (seagrass species richness and abundance). Terrestrial protection adjacent to seagrass meadows, defined as the absence of various anthropogenic land use perturbations, had significant positive effects on seagrass condition. The watershed area, and area of farmland and human development, had the most negative effect on seagrass condition. Using analysis of covariance and regression, we examined how marine protected area (MPA) establishment, size, and age, affected seagrass biotic conditions while holding environmental conditions constant. The relationship between biological and environmental canonical factors did not vary as a function of an MPA. This study provides evidence that land use is more important than marine protection for tropical seagrass condition. Our results demonstrate the complementary connection between land and sea, justifying the ‘ridge-to-reef’ approach in coastal conservation. Proper management of seagrasses should account for stewardship of the adjacent watersheds.

Organic carbon in seagrass sediments is influenced by seagrass canopy complexity, turbidity, wave height, and water depth

AbstractSeagrass meadows are important marine carbon sinks, yet they are threatened and declining worldwide. Seagrass management and conservation requires adequate understanding of the physical and biological factors determining carbon content in seagrass sediments. Here, we identified key factors that influence carbon content in seagrass meadows across several environmental gradients in Moreton Bay, SE Queensland. Sampling was conducted in two regions: (1) Canopy Complexity, 98 sites on the Eastern Banks, where seagrass canopy structure and species composition varied while turbidity was consistently low; and (2) Turbidity Gradient, 11 locations across the entire bay, where turbidity varied among sampling locations. Sediment organic carbon content and seagrass structural complexity (shoot density, leaf area, and species specific characteristics) were measured from shallow sediment and seagrass biomass cores at each location, respectively. Environmental data were obtained from empirical measurements (water quality) and models (wave height). The key factors influencing carbon content in seagrass sediments were seagrass structural complexity, turbidity, water depth, and wave height. In the Canopy Complexity region, carbon content was higher for shallower sites and those with higher seagrass structural complexity. When turbidity varied along the Turbidity Gradient, carbon content was higher at sites with high turbidity. In both regions carbon content was consistently higher in sheltered areas with lower wave height. Seagrass canopy structure, water depth, turbidity, and hydrodynamic setting of seagrass meadows should therefore be considered in conservation and management strategies that aim to maximize sediment carbon content.

What lies beneath: Why knowledge of belowground biomass dynamics is crucial to effective seagrass management

Conservation of seagrasses meadows is important, because these habitats are ecologically important and under threat. Monitoring and modelling are essential tools for assessing seagrass condition and potential threats, however there are many seagrass indicators to choose from, and differentiating between natural variability and declining conditions poses a serious challenge. Tropical seagrass meadows in the Indo-Pacific, in contrast to most temperate meadows, are characterized by a multi-species composition and a year-round growth. Differences in characteristics between species growing within one meadow could induce uncertainty in the assessment of the dynamics of these meadows if variation in productivity and related biomass turnover timescales are not taken into consideration. We present data on biomass distribution, production and turnover timescales of above- and belowground tissues for three key tropical seagrass species (Thalassia hemprichii, Cymodocea rotundata and Halodule uninervis) in two mixed-species meadows in the Spermonde Archipelago, Indonesia. Seagrass leaf turnover time scales were comparable for the three studied seagrass species and varied between 25 and 30 days. Variation in leaf and rhizome turnover timescales were small (or insignificant) between the two meadows. In contrast, rhizome turnover time scales were around ten times longer than leaf turnover timescales, and large differences in rhizome turnover time scales (200–500 days) were observed between the species. The late-successional species T. hemprichii had much slower rhizome turnover compared to the two early successional species. Furthermore, since rhizome biomass has a much longer turnover time compared to leaf biomass, changes in rhizome biomass reflect effects on seagrass meadows on a much longer timescale compared to changes in leaf biomass for these tropical meadows. We conclude that belowground biomass dynamics are an important proxy to assess long-term effects of environmental stressors on seagrass ecosystems and should be included in tropical seagrass management programmes.

The Great Barrier Reef World Heritage Area seagrasses: Managing this iconic Australian ecosystem resource for the future

The Great Barrier Reef World Heritage Area (GBRWHA) includes one of the world's largest areas of seagrass (35,000 km2) encompassing approximately 20% of the world's species. Mapping and monitoring programs sponsored by the Australian and Queensland Governments and Queensland Port Authorities have tracked a worrying decrease in abundance and area since 2007. This decline has almost certainly been the result of a series of severe tropical storms and associated floods exacerbating existing human induced stressors. A complex variety of marine and terrestrial management actions and plans have been implemented to protect seagrass and other habitats in the GBRWHA. For seagrasses, these actions are inadequate. They provide an impression of effective protection of seagrasses; reduce the sense of urgency needed to trigger action; and waste the valuable and limited supply of “conservation capital”. There is a management focus on ports, driven by public concerns about high profile development projects, which exaggerates the importance of these relatively concentrated impacts in comparison to the total range of threats and stressors. For effective management of seagrass at the scale of the GBRWHA, more emphasis needs to be placed on the connectivity between seagrass meadow health, watersheds, and all terrestrial urban and agricultural development associated with human populations. The cumulative impacts to seagrass from coastal and marine processes in the GBRWHA are not evenly distributed, with a mosaic of high and low vulnerability areas. This provides an opportunity to make choices for future coastal development plans that minimise stress on seagrass meadows.

The effect of ocean acidification on carbon storage and sequestration in seagrass beds; a global and UK context

Ocean acidification will have many negative consequences for marine organisms and ecosystems, leading to a decline in many ecosystem services provided by the marine environment. This study reviews the effect of ocean acidification (OA) on seagrasses, assessing how this may affect their capacity to sequester carbon in the future and providing an economic valuation of these changes. If ocean acidification leads to a significant increase in above- and below-ground biomass, the capacity of seagrass to sequester carbon will be significantly increased. The associated value of this increase in sequestration capacity is approximately £500 and 600 billion globally between 2010 and 2100. A proportionally similar increase in carbon sequestration value was found for the UK. This study highlights one of the few positive stories for ocean acidification and underlines that sustainable management of seagrasses is critical to avoid their continued degradation and loss of carbon sequestration capacity.

A Bayesian spatial approach for predicting seagrass occurrence

We implement a Bayesian spatial approach to predict and map the probability of occurrence of seagrass Posidonia oceanica at high spatial resolution based environmental variables. We found that depth, near-bottom orbital velocities and a spectral pattern of Landsat imagery were relevant environmental variables, although there was no effect of slope or water residence time. We generated a data inventory of P. oceanica samples at Palma Bay, NW Mediterranean, from three main sources: side scan sonar, aerial imagery and a customized drop-camera system. A hierarchical Bayesian spatial model for non-Gaussian data was used to relate presence-absence data of P. oceanica with environmental variables in the presence of spatial autocorrelation (SA). A spatial dimension reduction method, the predictive process approach, was implemented to overcome computational constraints for moderately large datasets. Our results suggest that incorporating spatial random effects removes SA from the residuals and improves model fit compared to non-spatial regression models. The main products of this work were probability and uncertainty model maps, which could benefit seagrass management and the assessment of the ecological status of seagrass meadows.

Influence of microhabitat on seedling survival and growth of the mediterranean seagrass posidonia oceanica (l.) Delile

Early life history phases are crucial stages limiting species distribution and abundance, thus influencing assemblage composition in marine benthic environments. In seagrass systems the period between seed germination and establishment is one of the most vulnerable phases for plant development. This study analyzes the influence of microhabitat structure, in terms of substrate nature and algal canopy, on the persistence and growth over two years of seedlings of Posidonia oceanica, the dominant Mediterranean seagrass. Long time persistence of seedlings only occurred on microhabitats providing vegetated rocky substrates, with a maximum value of 81% on rock covered by Cystoseira spp. No seedling was found on unvegetated sand and gravel after the first year. Seedling growth resulted increased on rock covered by Halopteris spp. and Dilophus spp. than on rock covered by Cystoseira spp. Results suggest that high canopy onto a stable substrate enhances seedling persistence, probably because these allow the best anchorage by roots while hampering water flow. In contrast, turf algal cover promotes better seedling growth, possibly through higher light irradiance and nutrient availability. Our findings support the view that the understanding of the factors controlling early life processes is a necessary prerequisite for the comprehension of seagrass species distribution patterns, colonization and recovery potentials, which, in turn, can guide sound strategies for seagrass management and restoration.

Komunitas Lamun di Pulau Barranglompo Makassar: Kondisi dan Karakteristik Habitat

Indication on seagrass decline has been observed in many places including Barranglompo Island of Makassar. Condition of damaged seagrass has significant impacts to the roles of seagrass as habitat, spawning ground, and feeding ground for various marine organisms and also role of seagrass as carbon absorbent and stocks. In order to provide a reference for appropriate seagrass management and conservation, it is required data on seagrass habitat. A research was done in Barranglompo Island, Makassar from December 2010 to November 2011. Seagrass condition was observed based on McKenzie et al . (2001) and Balestri et al . (2003). This research showed that large seagrass coverage was dispersed in southern, western and northern sides of the island. Meanwhile, seagrass spesies with wider distribution were E. acoroides, T. hemprichii and C.rotundata .

A comparison of threats, vulnerabilities and management approaches in global seagrass bioregions

Global seagrass habitats are threatened by multiple anthropogenic factors. Effective management of seagrasses requires information on the relative impacts of threats; however, this information is rarely available. Our goal was to use the knowledge of experts to assess the relative impacts of anthropogenic activities in six global seagrass bioregions. The activities that threaten seagrasses were identified at an international seagrass workshop and followed with a web-based survey to collect seagrass vulnerability information. There was a global consensus that urban/industrial runoff, urban/port infrastructure development, agricultural runoff and dredging had the greatest impact on seagrasses, though the order of relative impacts varied by bioregion. These activities are largely terrestrially based, highlighting the need for marine planning initiatives to be co-ordinated with adjacent watershed planning. Sea level rise and increases in the severity of cyclones were ranked highest relative to other climate change related activities, but overall the five climate change activities were ranked low and experts were uncertain of their effects on seagrasses. The experts’ preferred mechanism of delivering management outcomes were processes such as policy development, planning and consultation rather than prescriptive management tools. Our approach to collecting expert opinion provides the required data to prioritize seagrass management actions at bioregional scales.

An ecosystem‐scale predictive model of coastal seagrass distribution

Abstract Maintaining ecological processes that underpin the functioning of marine ecosystems requires planning and management of marine resources at an appropriate spatial scale. The Great Barrier Reef World Heritage Area (GBR) is the world's largest World Heritage Area (approximately 348 000 km2) and second largest marine protected area. It is difficult to inform the planning and management of marine ecosystems at that scale because of the high cost associated with collecting data. To address this and to inform the management of coastal (approximately 15 m below mean sea level) habitats at the scale of the GBR, this study determined the presence and distribution of seagrass by generating a Geographic Information System (GIS)‐based habitat suitability model. A Bayesian belief network was used to quantify the relationship (dependencies) between seagrass and eight environmental drivers: relative wave exposure, bathymetry, spatial extent of flood plumes, season, substrate, region, tidal range and sea surface temperature. The analysis showed at the scale of the entire coastal GBR that the main drivers of seagrass presence were tidal range and relative wave exposure. Outputs of the model include probabilistic GIS‐surfaces of seagrass habitat suitability in two seasons and at a planning unit of cell size 2 km×2 km. The habitat suitability maps developed in this study extend along the entire GBR coast, and can inform the management of coastal seagrasses at an ecosystem scale. The predictive modelling approach addresses the problems associated with delineating habitats at the scale appropriate for the management of ecosystems and the cost of collecting field data. Copyright © 2010 John Wiley & Sons, Ltd.

Calibration of a Bio-optical Model in the North River, North Carolina (Albemarle–Pamlico Sound): A Tool to Evaluate Water Quality Impacts on Seagrasses

Seagrasses are typically light limited in many turbid estuarine systems. Light attenuation is due to water and three optically active constituents (OACs): nonalgal particulates, phytoplankton, and colored dissolved organic matter (CDOM). Using radiative transfer modeling, the inherent optical properties (IOPs) of these three OACs were linked to the light attenuation coefficient, K PAR, which was measured in North River, North Carolina, by profiles of photosynthetically active radiation (PAR). Seagrasses in the southern portion of Albemarle-Pamlico Estuarine System (APES), the second largest estuary in the USA, were found to be light limited at depths ranging from 0.87 to 2 m. This corresponds to a range of K PAR from 0.54 to 2.76 m−1 measured during a 24-month monitoring program. Turbidity ranged from 2.20 to 35.55 NTU, chlorophyll a from 1.56 to 15.35 mg m−3, and CDOM absorption at 440 nm from 0.319 to 3.554 m−1. The IOP and water quality data were used to calibrate an existing bio-optical model, which predicted a maximum depth for seagrasses of 1.7 m using annual mean water quality values and a minimum light requirement of 22% surface PAR. The utility of this modeling approach for the management of seagrasses in the APES lies in the identification of which water quality component is most important in driving light attenuation and limiting seagrass depth distribution. The calibrated bio-optical model now enables researchers and managers alike to set water quality targets to achieve desired water column light requirement goals that can be used to set criteria for seagrass habitat protection in North Carolina.

Seagrass management in Indian River Lagoon, Florida: dealing with issues of scale

The major theme of this paper is that management of seagrass must deal with issues of geographic scale. Approaches at several scales are needed. Examples are drawn primarily from management programmes for the 250 km long Indian River Lagoon system on the south-east coast of Florida. The Lagoon has several attributes of spatial variation that require approaches at various scales (e.g., from 1:1 000 000 to 1:1). Risks and errors of scaling up and scaling down are described. For large-scale approaches, remote-sensing mapping methods are generally appropriate. In the Indian River Lagoon, true-colour aerial photographs. are typically taken every 2?3 years at 1 :24 000 scale. Such Lagoon-wide maps have fuzzy boundaries and cannot be scaled down to fine scale, but they can be scaled up. At large scale, seagrass restoration/protection targets (to a depth of 1.7 m) are reasonable, but are unreasonable at fine scale. For monitoring change within a bed or meadow at metre to 500 m scale, monitoring of fixed transects is a powerful tool. However, the technique has limited power for comparisons among beds, which requires multiple transects. To build a predictive model, a site-specific study examined the relationships among light, water quality, and seagrasses. The link between seagrass and water quality is made through a light attenuation model incorporating both water column and epiphytes. Extensive sampling is required to test the robustness of the model at all scales. No single scale is appropriate for all approaches, and no approach applies over all scales. If such considerations of scale are not incorporated, errors of measurement, inappropriate techniques for assessment, implementation of wrong solutions, and a lack of understanding of the system under study can result.