The impact of extreme weather events on the seagrass Zostera noltii and related Hydrobia ulvae population

Abstract

Coastal areas are typically subjected to a range of stressors, but they now face the additional stressor of climate change, manifested in part by an increased intensity and frequency of extreme weather events. Thus, the Mondego estuary (Portugal) has experienced organic enrichment (eutrophication) issues and these are potentially exacerbated by extreme weather events (floods, droughts and heat waves). In this paper, we explore the impact of interactions of these different stressors on the ecology of the system, specifically on the two key components, the seagrass Zostera noltii and the mud snail Hydrobia ulvae.Extreme events affected different components of the estuarine ecosystem (primary producers and macrofauna) differently. Whilst the floods directly impacted on H. ulvae, by wiping out part of its population, they did not directly affect the biomass of Z. noltii. In contrast, drought events, through their effects on salinity, directly impacted the biomass of Zostera, which had knock-on effects on the dynamics of H. ulvae.We conclude that over the period when the estuary experienced eutrophication, extreme weather events contributed to the overall degradation of the estuary, while during the recovery phase following the introduction of a management programme, those extreme weather episodes delayed the recovery process significantly.

Long-term climate-associated dynamics of a tropical seagrass meadow: implications for the future

“…This study has important implications for the future viability of intertidal seagrass meadows in the tropics, as many studies have inferred that some seagrass species under certain climate change scenarios could benefit from being released from carbon limitation (Palacios & Zimmerman 2007, Hall-Spencer et al 2008. Although this is a highly likely consequence of climate change for many seagrass species and meadows, the findings of our study support those of recent investigations (Campbell & McKenzie 2004, Campbell et al 2006, Waycott et al 2007, Cardoso et al 2008) to illustrate that future climate scenarios of higher air temperatures could also be highly detrimental to coastal and estuarine intertidal seagrass meadows. …”

“…The biomass of the small colonising species Halophila ovalis, which was a minor assemblage component, was positively correlated with rainfall; temperature was not a correlate with H. ovalis. Although incidences of high short-term rainfall and flooding have commonly resulted in detrimen- CSIRO 2007, Suppiah et al 2007 tal effects on seagrass meadows (Campbell & McKenzie 2004, Cardoso et al 2008, terrestrial water flows are important in supplying nutrients into coastal seagrass meadows (Short 1987, Udy et al 1999. Therefore, these findings are similar to those for temperate seagrasses (Marba & Duarte 1997) and suggest that the periods of drought that were experienced between 2002 and 2006, when the Norman River almost completely stopped flowing, may have been detrimental by not supplying sufficient nutrients to seagrass meadows.…”

“…Predictions of the influence of climate change scenarios on seagrass (Short & Neckles 1999, Harley et al 2006, Poloczanska et al 2007, Waycott et al 2007) are largely based on incidences of seagrass loss associated with extreme weather (Cardoso et al 2008, Micheli et al 2008 as reported in short-term experimental studies (Campbell et al 2006). Long-term studies directly measuring seagrass changes and how they are correlated with climate are rare.…”

“…Such meadows are often spatially expansive , Coles et al 2003 and are particularly important food sources for dugong Dugong dugong and green turtles Chelonia mydas (Bjorndal 1985, Preen & Marsh 1995. The intertidal and coastal location of these meadows makes them susceptible to large climatic events, such as flooding , Campbell & McKenzie 2004, drought (Cardoso et al 2008) and elevated temperature (Campbell et al 2006). Such meadows can be highly dynamic , McKenzie 1994, Rasheed 1999, and changes in assemblage biomass and plant growth can commonly vary by up to a factor of 4 (Brouns 1985, Erftemeijer & Herman 1994, Lanyon & Marsh 1995.…”

Characterization of a resilient seagrass meadow during a decline period

“…These factors might be related to the abundance and distribution of Hydrobia ulvae in zones with a high freshwater influence and the associations between Rissoa parva and Z. marina and between Bittium reticulatum and Z. noltei in areas with a high marine influence. Seagrasses are frequently characterized by the abundance of certain faunal groups (Cardoso et al 2008, Virnsten et al 1984. In La Barquería grazers dominate sites characterized by low hydrodynamics, stable sediment and relatively high tidal levels.…”