Seagrass-Watch Magazine Issue 47 - March 2013 | Page 2

In this issue: Article page Seagrass under pressure....................2 Boating impacts (Florida)....................7 Dredging impacts............................12 Dredging effects on food webs.......16 Pari Islands threats and restoration....18 Wakatobi seagrass loss & livelihoods..21 Trawling impacts (Mediterranean).....26 Paddock to Reef (Australia)...............31 Shipping (Torres Strait).....................34 Moorings (Porth Dinllaen, Wales)......36 Cornwall port (England)...................40 Davao Gulf threats (Philippines)........42 Girringun Rangers tracking change....44 Tourism development (Sri Lanka)......47 Macroalgae competition (India).........50 Nymphs of the sea..........................52 From the editors In this issue we take a timely look around our world at the impact we are having on our coastal waters. Unfortunately it is these same waters that are the home for seagrass meadows and in many places these meadows are paying the price for living too close to us. The pictures in this edition speak as loud as any words. The challenges are global –no one country is outstanding either in the problems and loss of seagrass or in finding manageable solutions. But it is not all bad news. Many initiatives seek to slow and halt the decline in this vital habitat. Risk mapping and working with farmers in Australia; managing vessel damage in Florida and Wales; restoration and working with local community and indigenous groups in Australia, Indonesia, and the Philippines, are all good examples. There is a role for us all in shaping public opinion and policy and we trust the articles in this issue will encourage useful discussion on positive approaches to a better world. COVER: Bait digging at Wynnum, Brisbane, Australia ISSN 1441-4236 Editors: Len McKenzie, Rudi Yoshida & Richard Unsworth Guest Editor: Rob Coles Proof reader: Louise Johns Layout & graphic design: Rudi Yoshida & Len McKenzie Recommended citation: McKenzie, LJ., Yoshida, RL., Unsworth, R. and Coles, R. (Eds) (2013) Seagrass-Watch magazine. Issue 47, March 2013. Seagrass-Watch HQ, Cairns. 52pp. DISCLAIMER: while all efforts have been made to verify facts, Seagrass-Watch HQ & TropWATER (James Cook University) take no responsibility for the accuracy of information supplied in Seagrass-Watch. The views expressed in this magazine are those of the authors and not necessarily those of SeagrassWatch HQ & TropWATER (James Cook University). Seagrass-Watch acknowledges the Traditional Owners on whose sea country we monitor Seagrass-Watch HQ (TropWATER) James Cook University, PO Box 6811 Cairns QLD 4870, AUSTRALIA email: [email protected] This magazine can be downloaded as a pdf from www.seagrasswatch.org/magazine.html Supporters major sponsors Department of Sustainability, Environment, Water, Population and Communities Great Barrier Reef Marine Park Authority seagrass under pressure Article by Rob Coles, Alana Grech & Len McKenzie Photography by Len McKenzie, Vedharajan Balaji & Helen Taylor Seagrass meadows are recognised as one of the most productive of the Earth's ecosystems(1,2). However, widespread and accelerating losses also place seagrass meadows among the most threatened(3), with almost 14% of all seagrass species considered at risk of extinction (three species are listed as Endangered)(4). Seagrass are most abundant in coastal regions where available nutrients, light and suitable habitable substrate meet growth requirements. It is also these coastal areas where seagrass are exposed to the impacts from the billion or more people who live within 50 km of them(5). These impacts have all led to a rapid loss of seagrass ecosystems, at a rate of around 1.5% of seagrass area per year(3). Worldwide seagrass ecosystems have been impacted or lost under the influence of direct and indirect effects of human activities(6,3). Direct impacts on seagrass from human activities causes immediate seagrass loss (e.g. removal of plants), while indirect impacts can be potentially more insidious due to their often widespread and chronic nature (e.g. overfishing of predators, which can cascade down the food web and lead to the loss of the herbivores that clean seagrasses of fouling algae, resulting in seagrass loss). Indirect impacts are also less obvious and the decline in seagrass can be slow (sometimes years or decades). Lastly, global climate change is acknowledged to possibly exacerbate these impacts and challenge local coastal management approaches. As a consequence of these losses, there is an urgent need to identify the threats to seagrass ecosystems. But identifying the threat is only the first step, as we also need to identify the human activity at the root of the problem. This will enable coastal managers to make informed decisions about where to best focus efforts to abate declines or develop solutions to minimise/reverse the decline. For example, the scientific literature lists excessive sediment and nutrients as the key cause of seagrass degradation, both acting to reduce available light to the seagrass plants. From a management perspective, however, that is not particularly helpful; we need to identify the human processes that cause reduction in light before advice can be given on how to make changes in our behaviour. Understanding the relationships between human activities a