Seagrass meadows are one of the major coastal ecosystems contributing to ‘Blue Carbon’ storage, alongside mangroves and tidal marshes. According to scientific literature, seagrass meadows and other equivalent coastal habitats capture 35 times more carbon than rainforests. Every square meter of a healthy seagrass meadow produces 20 lt of oxygen daily for the seas and the atmosphere. But what are the specific figures for Posidonia seagrass in the Aegean Sea? Understanding the capacity of seagrass to store carbon is critical to future research as a possible solution to mitigate global climate change. 

Archipelagos Institute in collaboration with expert scientists from the Biology Departments of the University of Essex and University of Portsmouth, UK carry out joint research aiming to quantify the capacity by which Posidonia seagrass meadows in the Aegean can sequester (i.e. capture) carbon. It examines how the seagrass meadows of different depths, densities, and other factors play a role in the sequestration of blue carbon. With the usage of specialized loggers, research so far has demonstrated that not all seagrass habitats are equal. If seagrass meadows are to play a role in mitigating CO2 emissions, variability in primary productivity within seagrass meadows needs to be accounted for to produce comprehensive autochthonous carbon sequestration estimates. By assessing the productivity of Posidonia meadows in the Aegean, we can estimate the extent to which these seagrass beds contribute to this valuable ecosystem service. Further, we can estimate the contribution to global warming in case carbon storage loses efficiency.

A key prerequisite for effectively managing and conserving the seagrass meadows is creating accurate maps which are essential for legislation enforcement. Given the poor quality of the official seagrass maps provided by the national authorities, it has become a priority for Archipelagos to generate detailed maps depicting the exact location of these protected habitats in as many marine regions as possible. 

In deeper waters, mapping is carried out via Archipelagos’ research vessel, the Aegean Explorer, using the multibeam sonar, a biomass scanner and several ROV systems. The multibeam provides information about the seafloor morphology, while the biomass scanner reveals the presence of benthic habitats and fish stocks. These advanced technologies offer valuable insight into the presence of seagrass habitats, resulting in high-resolution distribution maps.

For shallower waters, Archipelagos has developed a novel methodology collecting data with the use of kayaks that are equipped with sonar. In this way we map the presence of seagrass along predefined transects, while in combination with data collected from drones and satellite, the data collected by kayaks is used to create detailed habitat maps that depict the distribution of Posidonia meadows using Geographic Information Systems.

According to official data over 34% of the seagrass meadows in the Mediterranean have already been destroyed and even this is probably an underestimation of the true extent of the ongoing destruction. Due to their particularly slow growth rate (≅ 6cm / year) in combination with human impacts and the effects of climate change, when a Posidonia meadow is destroyed, it will take centuries to grow again. Therefore the efficient protection of those seagrass meadows that are still surviving is of utmost importance. 

Through targeted research projects, Archipelagos works to quantify the extent of the key factors of threat which include: uncontrolled anchorage, destructive fishing practices as well as intensive aquaculture. This research is essential in order to promote the enforcement of the existing national, EU and international legislation that is in place for the protection of seagrass meadows but is currently not being enforced. 

In Archipelagos we also work to develop tangible solutions and promote their protection, such as the design and piloting of sustainable mooring systems, as a solution to address the extensive damage caused by the uncontrolled anchorage of recreational boats, which every summer season results in the destruction of hundreds of square meters of seagrass meadows every day.

The Local Ecological Knowledge (LEK) of fishing communities in relation to environmental and ecological processes of their area is an invaluable source of information and data for Archipelagos’ researchers. This exchange of knowledge is made possible based on the relationship of mutual trust and cooperation with the local communities that Archipelagos has been developing for over two decades. 

For decades, Local Ecological Knowledge was ignored by the scientific community. Only recently the applicability of LEK data for mapping marine benthic habitats has become increasingly popular among scientists and environmental managers around the world. Unfortunately, there is limited information about which factors affect the quality of LEK as protocols for recording empirical data are yet to receive widespread use. 

Archipelagos research uses artisanal fishers’ LEK to map the distribution of Posidonia seagrass meadows in select Greek islands, while also developing research protocols that determine the quality of the LEK data through a comparison with remote sensing-based and other seagrass distribution data collected during the research surveys. This research also aims to provide a better understanding of which factors improve the quality of artisanal fishers’ LEK. Our research has shown that fishers’ LEK habitat maps can present a very high accuracy exceeding 90%, while the level of fishing experience is a direct indicator of the quality of empirical data. 

Archipelagos uses LEK to gather data and information for many species, habitats and anthropogenic activities. By joining forces we can help to bridge gaps between local stakeholders and scientists, by building community trust through nurturing an environment of collaboration towards the sustainable use of the ecosystem.

Posidonia seagrass meadows act as ecosystem architects, creating a habitat of fundamental importance which also acts as a shelter, nursery and feeding ground for over 1,300 species. Understanding the status of Posidonia meadows helps the Archipelagos Institute establish conservation strategies, inform the national stakeholders of the environmental status and prevent the degradation of this crucial ecosystem. 

Ιn various regions of the eastern Aegean Sea, Archipelagos researchers are undertaking studies on Posidonia meadow health and collect data following the Seagrass Watch protocol, as well as by assessing epiphyte cover and its relation with native and non-native seagrass species. We assess the health status of seagrass meadows by looking at various parameters: meadow patchiness, percentage cover of the seafloor, number of shoots, blade length, epiphyte cover of each leaf. Other environmental parameters such as the fish and invertebrate biodiversity around the meadow, the presence of non-native seagrass species and the levels of the various types of anthropogenic stressors are also important parts of our research.

Environmental DNA (eDNA) is becoming a popular tool for assessing total biodiversity as well as monitoring certain species in aquatic ecosystems. It uses traces of DNA left behind by species such as skin cells, mucus or other excretions to confirm their presence in certain locations, thus saving surveying effort and preventing misidentifications of similar-looking species. As hundreds of species may live sheltered within P. oceanica canopies, frequently visual census transects are not adequate to monitor their presence, therefore, eDNA could be the future of monitoring such cryptic or hidden species. 

Archipelagos Institute, in collaboration with the University of the West of England (UWE), has been working on developing this tool, initially focusing on macroinvertebrate species. However, with eDNA being such a new method, there is still very little known about how environmental factors influence the dispersal of eDNA, therefore, a large section of the work carried out by Archipelagos and UWE has been working on improving our understanding of this interaction, using as a case study species that live fixed to the seafloor.

The accumulation and biomagnification of plastic debris and microplastic pollutants is a dire global problem affecting nearly every marine ecosystem. The characteristic of seagrass meadows to attenuate the flow of water and waves, causes sedimentation of floating particles at higher rates compared to unvegetated areas as well as an increase in microplastic deposition within these canopies. Because of this, seagrass meadows have recently been recognized to have the potential to act as an important sink for microplastic pollution. 

Archipelagos Institute, Plymouth Marine Laboratory and the University of East Anglia are working together to investigate this theory by collecting seagrass blades and sediments from within the Posidonia seagrass meadows and extracting the microplastics to assess if there is an increase when compared to bare sand and other nearby marine habitats. Should our theory prove that more microplastics are found within the seagrass beds, it will highlight an important and, until now, overlooked microplastic sink, which could be causing serious impacts on the species which live within seagrass meadows.