Anthropogenic pressures and life history predict trajectories of seagrass meadow extent at a global scale

Seagrass meadows are threatened by multiple pressures, jeopardizing the many benefits they provide to humanity and biodiversity, including climate regulation and food provision through fisheries production. Conservation of seagrass requires identification of the main pressures contributing to loss and the regions most at risk of ongoing loss. Here, we model trajectories of seagrass change at the global scale and show they are related to multiple anthropogenic pressures but that trajectories vary widely with seagrass life-history strategies. Rapidly declining trajectories of seagrass meadow extent (>25% loss from 2000 to 2010) were most strongly associated with high pressures from destructive demersal fishing and poor water quality. Conversely, seagrass meadow extent was more likely to be increasing when these two pressures were low. Meadows dominated by seagrasses with persistent life-history strategies tended to have slowly changing or stable trajectories, while those with opportunistic species were more variable, with a higher probability of either rapidly declining or rapidly increasing. Global predictions of regions most at risk for decline show high-risk areas in Europe, North America, Japan, and southeast Asia, including places where comprehensive long-term monitoring data are lacking. Our results highlight where seagrass loss may be occurring unnoticed and where urgent conservation interventions are required to reverse loss and sustain their essential services. [Abstract copyright: Copyright © 2021 the Author(s). Published by PNAS.

Ocean current patterns drive the worldwide colonization of eelgrass (Zostera marina)

Currents are unique drivers of oceanic phylogeography and thus determine the distribution of marine coastal species, along with past glaciations and sea-level changes. Here we reconstruct the worldwide colonization history of eelgrass (Zostera marina L.), the most widely distributed marine flowering plant or seagrass from its origin in the Northwest Pacific, based on nuclear and chloroplast genomes. We identified two divergent Pacific clades with evidence for admixture along the East Pacific coast. Two west-to-east (trans-Pacific) colonization events support the key role of the North Pacific Current. Time-calibrated nuclear and chloroplast phylogenies yielded concordant estimates of the arrival of Z. marina in the Atlantic through the Canadian Arctic, suggesting that eelgrass-based ecosystems, hotspots of biodiversity and carbon sequestration, have only been present there for ~243 ky (thousand years). Mediterranean populations were founded ~44 kya, while extant distributions along western and eastern Atlantic shores were founded at the end of the Last Glacial Maximum (~19 kya), with at least one major refuge being the North Carolina region. The recent colonization and five- to sevenfold lower genomic diversity of the Atlantic compared to the Pacific populations raises concern and opportunity about how Atlantic eelgrass might respond to rapidly warming coastal oceans

Seagrass habitat characteristics of seahorses in selayar island, south sulawesi, indonesia

Seagrass beds are an important habitat for seahorses, a group of small-sized fishes that are named for the horse-like shape of their heads. This study paid attention to the role of seagrasses in seahorse occurrence and their size distribution because this habitat plays a crucial role in their life cycle providing food and shelter from predators. Seagrass characteristics of the habitat of two seahorses, Hippocampus barbouri and H. kuda, in Selayar Island were mapped and determined based on field observations. There were three main seagrass beds used as seahorse fishing grounds around the island, namely Labuang, Jahi-Jahi, and Binanga Benteng, with seagrass percentage cover of 33.14±2.44%, 29.02±1.90%, and 4.73±1.43%, respectively. Seagrass species occurring in the seahorse fishing areas were Enhalus acoroides, Thalassia hemprichii, Cymodocea rotundata, C. serrulata, Halophila ovalis, and Halodule uninervis. A high percentage cover of macroalgae (37.22±5.75%) was found in the seagrass beds of Binanga Benteng. Macroalgae found were Padina, Halimeda, and Dictyota. During the study, we found in total 142 individual H. barbouri and 19 H. kuda, with the highest abundance in the seagrass beds of Binanga Benteng followed by Jahi-Jahi, and the lowest abundance in Labuang. Moreover, the size of both male and female of H. barbouri was also consistently larger in Binanga Benteng, followed by Jahi-Jahi, and then Labuang, suggesting the importance of habitat complexity for this species. The male: female sex ratio was 1:1.2 for H. barbouri and 1:0.4 for H. kuda. In addition to the seagrass meadows, this study also revealed the importance of macroalgal beds in providing habitat for seahorses. This finding provides the basis for future research on the population status of two vulnerable species, H. barbouri and H. kuda in different seagrass habitat complexity in order to determine management priorities for conservation

Bycatch from seagrass fisheries: implication for conservation

Fishing activities conducted on seagrass bed to capture fishes and other seagrass associated fauna are very massive especially in the Pacific regions and undeveloped countries. This is due to the high abundance of economically important species associated to seagrasses, and additionally, seagrass area is the most accessible fishing ground throughout the year and with low capital. Seagrass meadows are importance habitat to support an abundance and diverse fish assemblages that form the basis for artisanal fisheries, which are vital in maintaining food security of coastal community in the regions. The seagrass fishery is considered a small-scale, multi-species and multi-gear fisheries. One of the fishing gear used in this fishery is traditional permanent fish trap called "sero". Bycatch from some small-scale fisheries have been reported such as from trawls, traps, gill nets, and longline fisheries. This study aimed to identify bycatch species from "sero", a type of seagrass fisheries which is in the form of fish fences with nets positioned on intertidal area of seagrass bed to the subtidal for approximately 200m. The result shown the bycatch from this fisheries was dominated by either low value fishes or invaluable and even toxic fishes for consumption, such as the puffers (Tetraodontidae and Diodontidae), juveniles of Apogonidae and Chaetodontidae. Additionally, sharks, turtles, and rays were also found in the bycatch. This result should be put into consideration as the bycatch would have an ecological consequences on the population, predator-prey relationship, and ecosystem resilience to stressor in general. Information from this study will be important for sustainable small-scale fisheries management and seagrass conservation, and therefore, further research into bycatch reduction in this fishery would be desirable