Experimental ecology and coastal conservation: conflicts on rocky shores

Hawkins, Stephen J.

doi:10.1002/(sici)1099-0755(199911/12)9:6<565::aid-aqc371>3.0.co;2-k

Cited by 8 publications

(6 citation statements)

References 32 publications

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“…Increases in the amount of time available for leisure are likely to lead to an increase in this form of disturbance by 2025. Recently concern has also been expressed about the levels of disturbance associated with scientific research in some locations (Hawkins 1999). Clearly there are trade-offs.…”

Section: Recreation Research and Educationmentioning

confidence: 99%

Rocky intertidal communities: past environmental changes, present status and predictions for the next 25 years

2002

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Rocky shores occur at the interface of the land and sea. Typically they are open ecosystems, with steep environmental gradients. Their accessibility to man has rendered them susceptible to a variety of impacts since prehistoric times. Access can be regulated, however, and they are more amenable to management than open ocean habitats. This review uses examples from throughout the world to demonstrate the extent to which rocky shores have been, and are currently, affected by pollution (examples used are endocrine disrupters, oil, eutrophication), over-collection of living resources, introduced alien species, modification of coastal processes (coastal defences, siltation) and global change (climate, sea level). These impacts are put into the context of natural fluctuations in time and variability in space of both the environment and the organisms. The relative magnitudes of some anthropogenic disturbances differ between the industrialized, developed world and the developing world. For example, in developed, industrialized countries pollution based impacts should diminish over the next 25 years due to improved regulation and a reduction in older ‘dirtier’ heavy industry. Conversely, in many developing countries pollution will increase as a consequence of growth in the human population and industrialization. Except for large-scale disasters such as oil spills, pollution tends mainly to influence embayed coastlines. Chronic effects such as eutrophication can have broader-scale impacts over whole coastlines and elevated nutrient levels have also been implicated in a trend of increasing frequency of catastrophic kills due to harmful algal. Direct removal of living resources has had major effects on coastlines at both local and regional scales and is likely to increase over the next 25 years, especially in developing countries where rapidly expanding human populations will put further pressure on resources. Impacts from recreational activities are likely to increase with greater leisure time in wealthier regions of the world, and cheaper travel will spread these impacts to poorer regions. Invasions by alien species have increased in frequency during the last 20 years leading to some dramatic effects on native assemblages. Problems associated with alien species, especially pathogens, will continue to increase over the next few decades. The proportion of the coastline modified by artificial structures (breakwaters, seawalls, groynes) will increase because of coastal development and defences against sea-level rise and the greater frequency of storms. This will increase connectivity between areas of rocky habitat. Siltation will continue to increase due to urbanization of catchments and estuaries, and changes in agricultural practice. This may have considerable impacts at local and regional scales, favouring sediment tolerant organisms such as turf algae and anemones. In the future, greater frequency of environmental extremes is likely, including large-scale events such as the El Niño Southern Oscillation (ENSO). Global change in temperature, sea-level rise and increases in the frequency of storms will affect rocky shores throughout the world, but this will occur over long time scales; over the next 25 years most of the responses by rocky shore communities will mostly be quite subtle. Thus rocky shores will be subject to increasing degradation over the next 25 years. They are, however, less vulnerable than many other aquatic habitats due to their hard substratum (rock), their relative lack of large biogenic structures and to their generally open nature. They are also remarkably resilient, and recovery can occur rapidly due to recruitment from unaffected areas. Their susceptibility to both terrestrial and marine disturbances does make them more vulnerable than sublittoral and offshore habitats. There are considerable gaps in knowledge, particularly of certain microhabitats such as crevices, boulders, sand-scoured areas and rock pools. These have been much less studied than more accessible assemblages on open, freely draining rock. More research is needed to establish the effects of increasing sediment loads, ultraviolet radiation and introduced species on rocky shore communities. Strategic and applied research programmes should integrate field experiments and carefully selected monitoring programmes to verify management regimes. Hindcasting from the palaeo-record would be valuable, to compare rates of predicted change with periods when change was rapid in the past. This information could, in principle, be used to help conserve rocky shores through networks of marine protected areas and a general reduction of environmental pollution.

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Section: Recreation Research and Educationmentioning

confidence: 99%

Rocky intertidal communities: past environmental changes, present status and predictions for the next 25 years

2002

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“…Crabs, fish, sea stars, birds, humans and even small rodents are considered to be important predators of intertidal prey on Atlantic and Pacific shores such as limpets, mussels and barnacles by controlling their abundance and distribution (Navarrete & Castilla, 1993; Norberg & Tedengren, 1995; Castilla, 1999; Coleman et al , 1999; Carlton & Hodder, 2003; Rius & Cabral, 2004; Monteiro et al , 2005; Cannicci et al , 2007; Markowska & Kidawa, 2007). In turn, these prey are known to be key space occupiers; their absence or reduced abundance will strongly influence intertidal community composition (Hawkins, 1999; Hawkins et al , 2000; Boaventura et al , 2002a; Cannicci et al , 2002). Patellid limpets are the most common limpets on Portuguese shores (Boaventura et al , 2002a) and are considered to be dominant grazers, playing a key role on European rocky shores by controlling algae abundance and distribution (Hawkins, 1999).…”

Section: Introductionmentioning

confidence: 99%

Predation: a regulating force of intertidal assemblages on the central Portuguese coast?

2009

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Predation has long been recognized as an important biological force driving community patterns in intertidal rocky shores throughout the world. Little is known, however, about the role of predation by mobile marine predators in shaping intertidal prey populations in Portuguese rocky shores. The abundance and population structure of crabs were assessed during nocturnal low-tides on two rocky shores to characterize potential predator species. To assess the effect of predation on intertidal species including limpets, barnacles and mussels, predator exclusion experiments using full cage, partial cage and no cage treatments, were set up for two months on two shores on the central Portuguese coast. Pachygrapsus marmoratus (Fabricius) and Eriphia verrucosa (Forsskål) were the most abundant crabs. Results from predator exclusion experiments suggested that predators do not exert a significant control on abundance of limpets, mussels or barnacles on the midshore during the experimental period. Despite the fact that these crabs are known to feed on the analysed prey, several factors may account for the observed absence of impact on prey abundance and these are discussed.

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“…Over the last two decades, ecology has changed from a largely qualitative discipline to a quantitative hypothesis-driven experimental science and manipulative field experiments have contributed greatly to ecological theory during this period (Hawkins, 1999). Rocky shores, in particular, have proved to be good testing ground for ideas of general ecological significance (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Rocky shores, in particular, have proved to be good testing ground for ideas of general ecological significance (e.g. Connell and Slatyer, 1977;Benedetti-Cecchi and Cinelli, 1996;Dye, 1998;Hawkins, 1999;Olobarria, 2002;Hutchinson and Williams, 2003).…”

Section: Introductionmentioning

confidence: 99%

Ecological indicators performance during a re-colonisation field experiment and its compliance with ecosystem theories

Patrício

Salas

Pardal

et al. 2006

Ecological Indicators

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Through a re-colonisation field experiment three main questions were approached: (1) How do different ecological indicators react during the process of recovery? (2) What does grow first during a community succession, biomass or complexity? (3) Can the chosen ecological indicators help in recognising the three proposed forms of growth: biomass, network and information, throughout re-colonisation?The study was carried out in an intertidal rocky community dominated by the algae Corallina elongata. Experimental plots were cleared and macroalgae and fauna were removed. Multivariate analysis was performed to examine the convergence of the disturbed plots with the surrounding community during recovery. Shannon-Wiener Index, Margalef Index, Pielou evenness, Eco-Exergy and Specific Eco-Exergy were applied to characterise the state of the community during the process. Results show that the replacement of species over time happens both with the macroalgae and associated macrofauna community. Species richness increased rather rapidly and species composition was similar in disturbed and undisturbed areas. After 7 months, diversity was consistently higher in the community undertaking recovery. Eco-Exergy and Specific Eco-Exergy provided useful information about the structural development of the community but lacked discriminating power with regard to the informational status of the system. The observations appear to illustrate a case explainable by the Intermediate Disturbance Hypothesis (IDH). Overall, the characteristics of a systems' recovery after disturbance appear to be dependent on the spatial scale of the disturbance. If a disturbed area is small when compared to a contiguous non-disturbed one, complexity (information and network) will recover prior to biomass. #

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Experimental ecology and coastal conservation: conflicts on rocky shores

Cited by 8 publications

References 32 publications

Rocky intertidal communities: past environmental changes, present status and predictions for the next 25 years

Rocky intertidal communities: past environmental changes, present status and predictions for the next 25 years

Predation: a regulating force of intertidal assemblages on the central Portuguese coast?

Ecological indicators performance during a re-colonisation field experiment and its compliance with ecosystem theories

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