Loss Of Seagrass Meadows Research Articles

Rapid sea level rise causes loss of seagrass meadows

As global declines in seagrass populations continue to cause great concern, long-term assessment of seagrass meadows show promise in furnishing valuable clues into fundamental causes of seagrass loss and drivers of environmental change. Here we report two long-term records of seagrass presence in western Gulf of Mexico coastal waters (Laguna Madre) that provided insight into their rapid decline in a relatively pristine ecosystem. Coincident with unprecedented increases in water depth starting in 2014 (14–25 mm y−1), monthly measurements at a deep edge fixed station revealed that two ubiquitous seagrass species (Halodule wrightii and Syringodium filiforme) vanished altogether in just five years; a subsequent basin-wide assessment revealed that seagrasses disappeared at 23% of 144 sentinel stations. Models that incorporate differing sea level rise scenarios and water depth thresholds reveal potential global losses of seagrass habitat (14,000 km2), with expansion into newly created shallow habitats constrained by altered natural shorelines.

Why seagrass meadows should be protected

Marine Ecology Seagrasses are found along coastlines around the world but are under threat from human activities. In a Perspective, Cullen-Unsworth and Unsworth explain that seagrasses perform many important functions. For example, seagrasses provide a habitat for diverse marine species, including numerous commercial fish species, and store large amounts of carbon. Loss of seagrass meadows may thus contribute to rising carbon emissions and may threaten biodiversity and food security. Research into the extent and properties of seagrass meadows is helping to inform conservation efforts, but time is of the essence to avoid further losses of these important ecosystems. Science , this issue p. [446][1] [1]: /lookup/doi/10.1126/science.aat7318

Linking pipefishes and seahorses to seagrass meadows in the Venice lagoon: Implications for conservation

Abstract Seagrass meadow degradation and loss is one of the major threats to fish biodiversity in coastal marine and lagoon ecosystems in the Mediterranean. Pipefishes and seahorses (family Syngnathidae) are particularly affected by loss of seagrass meadows and other structured habitats, on which they rely for survival and reproduction. Despite their charismatic appearance and peculiar behaviour, their habitat ecology is still poorly understood in Mediterranean coastal waters. This study focuses on syngnathid assemblage composition and diversity in the shallow waters of the Venice lagoon (Italy), aiming at highlighting habitat preferences and providing insights into the conservation of biodiversity in these ecosystems. Generalized Additive Models were used in order to disentangle the potential effect of habitat typologies and different architectures of seagrass meadows from that of other environmental parameters. Most abundant taxa and whole syngnathid assemblage indicators were positively associated with seagrass meadows. Only few species, however, were seagrass specialists in shallow waters, and preferred meadows with taller canopies. Despite that, other structured habitats including short‐leaved seagrass meadows and macroalgal beds were important for some species and overall assemblage diversity. Managers in Mediterranean coastal lagoons should thus limit human pressures that lead to the depletion of seagrass meadows, with particular attention to long‐ and broad‐leaved species in less confined areas. Nevertheless, syngnathid assemblages would benefit from the preservation and restoration of the overall habitat diversity characterizing shallow waters in coastal lagoon. Future studies should aim at investigating the potential role of habitats at greater depths in supporting syngnathids.

Restoration of the Seagrass Amphibolis antarctica—Temporal Variability and Long-Term Success

The loss of seagrass meadows is an increasing problem worldwide. The important role that these meadows play in coastal ecosystems has resulted in substantial attention to the development of seagrass restoration techniques. Here, I present long-term (up to 5 years) results of seagrass restoration off the coast of Adelaide, South Australia, where >5,000 ha of seagrass has been lost and where trials of traditional restoration techniques using seeds and transplants have failed due to high levels of sand and water movement. Hessian (burlap) sandbags were deployed bimonthly (with some interruptions) from November 2007 to November 2012 (a total of 24 deployments), with a mix of single- and double-layered bags, to provide a stable substrate for naturally occurring Amphibolis seedlings to recruit to. At the end of the study (January 2013), bags deployed in August 2009 had similar stem densities to those found in adjacent natural meadows (15.2 ± 1.4 (SE) vs 18.6 ± 2.5). Bags deployed in May 2008 and August 2011 had 12.8 ± 2.3 and 13.2 ± 2.2 stems, respectively. Furthermore, stem lengths on older bags were greater than those on natural meadows (42.1 ± 4.2 after 62 months vs 30.2 ± 1.5 cm). While there was some interannual variation in recruitment success, the strongest predictor of success was deployment month. Bags deployed outside the austral winter recruitment season did not retain the ability to catch a large number of recruits, indicating that any restoration using this technique will have to be undertaken between approximately May and August to maximize chances of success.

Outstanding appearance of Ruppia maritima along Baja California Sur, México and its influence in trophic networks

Human impact and global warming are driving major modifications to the world’s ecosystems, the coastal zone being one of the most damaged. Seagrass meadows constitute coastal communities that have experienced great losses worldwide. The dominant seagrass in the meadows of the Pacific coast of North America is Zostera marina. There is evidence that Z. marina has been replaced in some places by the opportunistic seagrass Ruppia maritima with important implications for the trophic connections of local ecosystems. In Mexico, there are few reports on the distribution and loss of seagrass meadows. Here, we report on the importance that R. maritima has gained in three wetlands of northwest Mexico, replacing Z. marina and modifying local trophic networks. We made extensive samplings on Z. marina and R. maritima meadows, recording shoot density and marking their spatial distribution with GPS. We included information on the presence of R. maritima at other wetlands of northwest Mexico from historical reviews and current sampling. R. maritima was recorded in 29 localities, 3 of which are new records. Their shoot density and spatial coverage were highest in late fall and decreased in late spring, while Z. marina meadows increased after the reduction of R. maritima meadows. R. maritima now constitutes a primary food source for green turtles in the sampled wetlands, something unprecedented a few years ago. Improvement of wetland management plans is needed to stop environmental degradation, R. maritima invasion, and the loss of ecosystem functions.

The Dugong, Dugong dugon, in Egyptian waters: distribution, relative abundance and threats

This paper presents the results of an interview survey used to identify the distribution and relative abundance of Dugongs (Dugong dugon) in Egypt’s Red Sea during 2001, 2002 and 2003. The survey area ranged from Hurghada, immediately south of the Gulf of Suez, to El Shalatin, about 200 km north of the Sudan border. Respondents, such as fishermen, were asked preprepared questions to determine the number of Dugongs observed per sighting, the length class of individuals, the month of observation and the location. Important feeding habitat, defined in part by the presence of Dugong feeding trails, was identified during a concurrent seagrass survey. Dugongs occurred throughout the survey area, but apparently in very low numbers. The maximum and minimum numbers reported were 17 in 2002 and 12 each in 2001 and 2003. Some individuals may have been counted more than once per annum. There was no evidence of annual change in the number of Dugong sightings, but a statistically greater number of sightings was made in summer compared with winter. Two hypotheses are proposed to explain this variation, but they are not mutually exclusive. The first is that Dugongs undertake winter movements to warmer waters. The second is that winter sea conditions made it harder to observe Dugongs. Important feeding habitat in the Wadi El Gemal Hamata Protected Area was confirmed by the presence of Dugong feeding trails in seagrass meadows. Known and predicted threats to this species in Egypt are loss of seagrass meadows, net entrapment and boat strikes.