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.

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