Guidelines for model adaptation: a study of the transferability of a general seagrass ecosystem DBN model

Ecological models are extensively and increasingly used in support of environmental policy and decision making. Dynamic Bayesian Networks (DBN) as a tool for conservation have been demonstrated to be a valuable tool for providing a systematic and intuitive approach to integrating data and other critical information to help guide the decision-making process. However, data for a new ecosystem are often sparse. In this case, a general DBN developed for similar ecosystems could be applicable, but this may require the adaptation of key elements of the network. The research presented in this paper focused on a case study to identify and implement guidelines for model adaptation. We adapted a general DBN of a seagrass ecosystem to a new location where nodes were similar, but the conditional probability tables varied. We focused on two species of seagrass (Zostera noltei and Z. marina) located in Arcachon Bay, France. Expert knowledge was used to complement peer-reviewed literature to identify which components needed adjustment including parameterisation and quantification of the model and desired outcomes. We adopted both linguistic labels and scenario-based elicitation to elicit from experts the conditional probabilities used to quantify the DBN. Following the proposed guidelines, the model structure of the DBN was retained, but the conditional probability tables were adapted for nodes that characterised the growth dynamics in Zostera spp. population located in Arcachon Bay, as well as the seasonal variation on their reproduction. Particular attention was paid to the light variable as it is a crucial driver of growth and physiology for seagrasses. Our guidelines provide a way to adapt a general DBN to specific ecosystems to maximise model reuse and minimise re-development effort. Especially important from a transferability perspective are guidelines for ecosystems with limited data, and how simulation and prior predictive approaches can be used in these contexts.

Estimation of carbon stock in seagrass communities in Central Tapanuli

This study aims to determine the carbon stock in seagrass communities in Central Tapanuli, North Sumatera, Indonesia. The research was conducted from July to August 2020 in the coastal areas of Hajoran and Jago Jago. The parameters measured in this study were density, coverage, biomass, carbon content, and carbon stock in seagrass. Biomass analysis and carbon measurement are divided into the top (above-ground biomass) and the bottom substrate (below-ground biomass). Carbon measurements are conducted using the loss on ignition (LOI) approach. The results showed that the seagrass ecosystem on the coast of Central Tapanuli Regency, which was covered by monospecies Enhalus acoroides, was in a less healthy condition with a cover percentage of 30.3-33.3% and a density of 59-67 shoots/m2. Above-ground and below-ground seagrass biomass reached 140.19-188.72 g/m2 and 368.13-423.69 g/m2 respectively, while carbon stock reached 70.57-94.86 g Corg/m2 and 18731-19603 g Corg/m2 and total standing stock range 257.87-290.90 g Corg/m2. The data obtained from this research can be used as a database to see the potential of seagrass beds as storage of CO2 and as an effort to mitigate and adapt to climate change.

The sustainability of the diversity of marine macrofauna associated with seagrass through ecotourism in The Mandalika Exclusive Economic Zone Lombok Island, Indonesia

Ecotourism activities play an essential role in protecting and managing natural habitats and the species found in the habitat and creating economic benefits for the surrounding community. However, some parties state that ecotourism has a negative effect on the environment if it does not correctly follow the area’s rules and the ecotourism activities are not monitored and appropriately assessed. The objective of this study were : (i) to evaluate the diversity of seagrass and associated macrofauna at the Kuta ecotourism site in the Mandalika area of Lombok Island Indonesia and (ii) to know the response of the surrounding community and stakeholders in terms of the role of ecotourism in supporting the sustainability of the seagrass ecosystem in its function as an important factor in maintaining the diversity of marine macrofauna in the area. Data collection methods related to seagrass diversity and associated biota (Bivalves and Echinoderms) were carried out using the line transect method and the quadrat method. Meanwhile, the perception and response data of the community was obtained through observation and interviews. Data analysis was carried out in a qualitative descriptive manner. The results showed that there were 8 species of seagrass found. Seagrass species Syringodium isoetifolium and Cymodocea rotundata have the highest density of about 18.48 ind/m2, and Enhalus acoroides has the highest area of coverage, which is around 16.41 ind/m2. The highest macrofauna diversity was fish (10 families with 16 species) followed by Echinoderms (7 families with 9 species), and Bivalves (5 families with 7 species). Respondents in the fishermen category showed their understanding that ecotourism in their area plays an important role in supporting the sustainability of seagrass ecosystems, and this condition affects maintaining the diversity of associated marine macrofauna. This is supported by the findings that there has been a transition in the use of marine biota fishing gear, namely from the use of tools/methods that are not environmentally friendly to the use of tools/methods that are environmentally friendly. The most encouraging thing is that the use of bombs has completely stopped after ecotourism started in their area. Thus, it can be concluded that the existence of ecotourism in the Mandalika has had a positive influence on the behavior of fishing communities, especially in maintaining the seagrass ecosystem which is important in supporting the sustainability of marine macrofauna biodiversity in the Mandalika, South Coast of Lombok, Indonesia.

Association patterns of seagrass with gastropods types in the intertidal zone of coastal waters, Suli village, Salahutu district, Ambon island

Seagrass beds play an important role in coastal aquatic ecosystems and are one of the tidal areas that are widely used by the community as a forum for the interests of educational institutions in research activities, conservation of various marine biota. Ecologically, the seagrass ecosystem acts as a shelter and a place to eat various marine biota, including gastropods. The purpose of this research is not only to explore the diversity of gastropods, but also to examine the interactions of gastropod species, both between the same species and between different species in a community of seagrass ecosystems. The diversity index calculation shows the diversity index value H = 3.982 > 3, this means that the diversity of gastropod species is quite good. The results of the basic analysis obtained the calculated X2 value of 0.656, > X2 table with a significant level of 0.05%. There is an association relationship between seagrass ecosystems and the types of gastropods that live in seagrass ecosystems in coastal waters of Suli Village, Ambon. Keywords: Gastropods, Seagrass meadows, Association

Dynamics of Nutrients and Colored Dissolved Organic Matter Absorption in a Wetland-Influenced Subarctic Coastal Region of Northeastern Japan: Contributions From Mariculture and Eelgrass Meadows

Coastal oceans interacting with terrestrial ecosystems play an important role in biogeochemical cycles. It is therefore essential to research land–ocean interactions for further understanding of the processes influencing nutrients dynamics in coastal areas. We investigated the seasonal and spatial distribution of nutrient concentrations and light absorption coefficients of colored dissolved organic matter (CDOM), non-algal particles (NAP), and phytoplankton in a wetland-influenced river–eelgrass meadows–coastal waters continuum in the protected and semi-enclosed coastal sea of Akkeshi-ko estuary (AKE) and Akkeshi Bay (AB), Japan from April 2014 to February 2015. The mixing dilution lines of the CDOM absorption coefficient at 355 nm [aCDOM(355)] relative to salinity predicted by two end-members between freshwater and coastal water showed conservative mixing in AB. Silicate concentrations were significantly correlated with salinity and aCDOM(355) in AB in each month except for December 2014. These results suggest that silicate and CDOM in AB primarily originates from wetland-influenced river discharge. However, samples collected from the eelgrass meadows of AKE, where mariculture is developed, showed non-conservative mixing of silicate concentrations and aCDOM(355) with salinity except for June 2014. Elevated phosphate concentrations, probably released from sediments, were also found in the eelgrass meadows of AKE, especially during summer. These results suggest that the metabolic activities of mariculture and seagrass ecosystem significantly contribute to the nutrient cycles and CDOM absorption in AKE and to the distinct water-mass systems inside and outside AKE. The relative absorption properties of NAP [aNAP(443)], phytoplankton [aph(443)], and aCDOM(443) showed that CDOM is the main factor affecting the light distribution in AKE. However, the relative absorption properties varied seasonally in AB because of spring and autumn phytoplankton blooms and ice cover during winter. Significant relationships were observed between the Secchi disk depth (ZSD), aNAP(443), and aCDOM(443). Chl a concentration and aph(443) were not good indicators for predicting ZSD in our study region. These results suggest that incorporating inherent optical properties and CDOM from mariculture and seagrass ecosystem into ecosystem models could improve predictions of light distribution along the freshwater–eelgrass–coastal waters continuum in optically complex coastal waters.

Feeding ground indications are based on species, seagrass density and existence of Dugong dugon in Hiri Island Sea, North Maluku, Indonesia

Seagrass ecosystems are located between mangrove ecosystems and coral reefs. Seagrass ecosystems are habitats and foraging area for many marine organisms. Eco-biological cycles in seagrass ecosystems are important for maintaining populations of many organisms. Seagrass at Hiri Island is distributed horizontally along the coast. This island is also a location where Dugong dugon is found North Maluku. Dugong dugon is a vurneable species that has been included in the IUCN and Appendix I Cites. This study aimed to identify species, density of seagrass and existence of Dugong dugong. The survey method used quadratic transect method to collect seagrass data. The Results found 6 species of seagrass at Hiri Island. Five species of those seagrass (Cymodocea serrulata, Cymodecea rotundata, Halodule uninervis, Halodule pinifolia, Halophila spinulosa) are known as food of Dugong dugon. The highest species density was shown by Halodule uninervis. The presence of Dugong dugon and its feeding trail was found during field survey. Information on seagrass species and Dugong dugon sightings location can be used for endangered species conservation policies. Management and conservation efforts need to be done to maintain seagrass ecosystem and Dugong dugon potential habitat at Hiri Island.

Trait gradients inform predictions of seagrass meadows changes to future warming

Comparing populations across temperature gradients can inform how global warming will impact the structure and function of ecosystems. Shoot density, morphometry and productivity of the seagrass Posidonia oceanica to temperature variation was quantified at eight locations in Sardinia (western Mediterranean Sea) along a natural sea surface temperature (SST) gradient. The locations are spanned for a narrow range of latitude (1.5°), allowing the minimization of the effect of eventual photoperiod variability. Mean SST predicted P. oceanica meadow structure, with increased temperature correlated with higher shoot density, but lower leaf and rhizome width, and rhizome biomass. Chlorophyll a (Chl-a) strongly impacted seagrass traits independent of SST. Disentangling the effects of SST and Chl-a on seagrass meadow shoot density revealed that they work independently, but in the same direction with potential synergism. Space-for-time substitution predicts that global warming will trigger denser seagrass meadows with slender shoots, fewer leaves, and strongly impact seagrass ecosystem. Future investigations should evaluate if global warming will erode the ecosystem services provided by seagrass meadows.