Quantification and classification of the main environmental impacts on a Halodule wrightii seagrass meadow on a tropical island in northeastern Brazil

Abstract

Multiple stress mechanisms have caused a worldwide decrease in seagrasses, which are vulnerable to environmental and/or anthropogenic pressure. The loss of seagrass meadows of Halodule wrightii is reported for the littoral of Itamaracá Island (Northeastern Brazil). The present study identified the main anthropogenic factors that negatively influenced over the abundance and distribution of seagrass meadows between July and September 2007 at the Jaguaribe and Pilar Beaches, Eastern littoral of Itamaracá. Anthropogenic impact included the discharge of untreated sewage through fluvial channels, urban and commercial development along the coast, the anchoring of motorized and non-motorized boats, diverse fishing techniques and the dumping of solid waste. The data indicates that the Pilar is an environment with a higher impact index (71.43%) when compared with the Jaguaribe (57.14%), standing out the number of boats with a central motor, the total number of boats, the presence of shellfish gatherers and coastal urban development. The present study reinforces the need for defining management and conservation measures for this ecosystem, which has high ecological and economic value.

The response of the seagrass Halodule wrightii Ascherson to environmental stressors

“…Each of the seagrass meadow sites were categorized in terms of environmental impacts. This used a scoring system developed by the authors based on methods and evidence identified from previous studies to provide an index (Creed and Oliveira, 2007;Jones and Unsworth, 2016;Oigman-Pszczol and Creed, 2011;Pitanga et al, 2012) including information collected based on site observations. The anthropogenic impacts that were included in the calculation of this index were as follows, included vicinity to highly urbanized area, population, industry, agriculture, boat activity, tourism, freshwater input/sewage outfall, turbidity and enclosed water body/proximity to open sea.…”

“…This suggests environmental factors are affecting the morphology and the development or expansion of these seagrasses. Factors such as high sediment instability, low temperatures, strong wave action at low tides or exposure to air have been described as some of the potential factors that limit the existence of H. wrightii (Barros et al, 2013), although such drivers remain poorly explored (Creed, 1997;Creed and Amado Filho, 1999;Pitanga et al, 2012). Direct observations of environmental effects on Brazilian seagrasses are limited (Barros et al, 2013), with data such as leaf nutrient content and photophysiological attributes lacking in the literature.…”

Threats to Seagrass Ecology and Indicators of the Importance of Seagrass Ecological Services in the Coastal Waters of East Lombok, Indonesia

“…Nevertheless, the increasing human impacts associated with eutrophication and it is possible that could exacerbate seagrass loss (Coll et al, 2011;Stoner et al, 2014). This indicates that, the anthropogenic factors that negatively influenced over the abundance and distribution of seagrass, through fluvial channels, urban and commercial development, the anchoring of motorized and non-motorized boats, diverse fishing techniques and the dumping of solid waste (Pitanga et al, 2012), as though, seagrass in the Western Pacific are showing signs of stress and decline due to human impacts, despite the vastness of the ocean area and relatively low development pressure (Short et al, 2014).…”

Seagrass, bioindicator, light, water quality, Zostera marina, Zostera noltii, Halodule wrightii, monitoring, Chlorophyll fluorescence, stable isotope, nutrients.

“…Each of the seagrass meadow sites were categorized in terms of environmental impacts. This used a scoring system developed by the authors based on methods and evidence identified from previous studies to provide an index (Creed and Oliveira, 2007;Oigman-Pszczol and Creed, 2011;Pitanga et al, 2012) including information collected based on site observations. The anthropogenic impacts that were included in the calculation of this index were as follows; vicinity to highly urbanized area, population, industry, agriculture, boat activity, tourism, freshwater input/sewage outfall, turbidity and enclosed water body/proximity to open sea.…”