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Loss and recovery potential of marine habitats: an experimental study of factors maintaining resilience in subtidal algal forests at the Adriatic sea.

Perkol-Finkel S, Airoldi L - PLoS ONE (2010)

Bottom Line: Lack of surrounding adult canopies did not seem to impair the potential for assisted recovery, suggesting that in these systems recovery could be actively enhanced even following severe depletions.Moreover, we demonstrate that the mere restoration of environmental conditions preceding a loss, if possible, may be insufficient for ecosystem restoration, and is scarcely cost-effective.We conclude that the loss of complex marine habitats in human-dominated landscapes could be mitigated with appropriate consideration and management of incremental habitat changes and of attributes facilitating system recovery.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Biologia Evoluzionistica Sperimentale and Centro Interdipartimentale di Ricerca per le Scienze Ambientali, University of Bologna, Ravenna, Italy. sperkol@gmail.com

ABSTRACT

Background: Predicting and abating the loss of natural habitats present a huge challenge in science, conservation and management. Algal forests are globally threatened by loss and severe recruitment failure, but our understanding of resilience in these systems and its potential disruption by anthropogenic factors lags well behind other habitats. We tested hypotheses regarding triggers for decline and recovery potential in subtidal forests of canopy-forming algae of the genus Cystoseira.

Methodology/principal findings: By using a combination of historical data, and quantitative in situ observations of natural recruitment patterns we suggest that recent declines of forests along the coasts of the north Adriatic Sea were triggered by increasing cumulative impacts of natural- and human-induced habitat instability along with several extreme storm events. Clearing and transplantation experiments subsequently demonstrated that at such advanced stages of ecosystem degradation, increased substratum stability would be essential but not sufficient to reverse the loss, and that for recovery to occur removal of the new dominant space occupiers (i.e., opportunistic species including turf algae and mussels) would be required. Lack of surrounding adult canopies did not seem to impair the potential for assisted recovery, suggesting that in these systems recovery could be actively enhanced even following severe depletions.

Conclusions/significance: We demonstrate that sudden habitat loss can be facilitated by long term changes in the biotic and abiotic conditions in the system, that erode the ability of natural ecosystems to absorb and recover from multiple stressors of natural and human origin. Moreover, we demonstrate that the mere restoration of environmental conditions preceding a loss, if possible, may be insufficient for ecosystem restoration, and is scarcely cost-effective. We conclude that the loss of complex marine habitats in human-dominated landscapes could be mitigated with appropriate consideration and management of incremental habitat changes and of attributes facilitating system recovery.

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Natural changes in density of recruits:Average densities (±1 SE, n = 15, 5 sub-quadrats of 6×6 cm from each of 3 plots of 30×30 cm) of C. barbata recruits of on large (>4 m3) marked boulders from July 2008 to February 2009 at Due Sorelle (black) and La Vela (purple).
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pone-0010791-g005: Natural changes in density of recruits:Average densities (±1 SE, n = 15, 5 sub-quadrats of 6×6 cm from each of 3 plots of 30×30 cm) of C. barbata recruits of on large (>4 m3) marked boulders from July 2008 to February 2009 at Due Sorelle (black) and La Vela (purple).

Mentions: We found virtually no recruits neither underneath canopies of Cystoseira nor in any other of the dominant habitats comprising mussel beds, stands of simpler seaweeds, or mixed mosaics of the two. In all these habitats recruits, if any, occurred only very sporadically (<1 recruits per 2.5 m2). However, at both sites we found occasional patches of extremely dense recruits of Cystoseira, reaching up to >90% cover (Fig. 4) and densities as high as 16 juveniles per 6×6 cm sub-quadrat (Fig. 5). These patches of recruits were mainly confined to shallow boulders otherwise generally covered by thin filamentous turfs or other small ephemeral algae. On average, cover and density of recruits were highest at Due Sorelle (significant effect of factor Site for cover, F1,8 = 15.97, P<0.01), and based on our transects we estimated they accounted for 5 to 8% of the surveyed area at La Vela and Due Sorelle, respectively (Fig. 2a).


Loss and recovery potential of marine habitats: an experimental study of factors maintaining resilience in subtidal algal forests at the Adriatic sea.

Perkol-Finkel S, Airoldi L - PLoS ONE (2010)

Natural changes in density of recruits:Average densities (±1 SE, n = 15, 5 sub-quadrats of 6×6 cm from each of 3 plots of 30×30 cm) of C. barbata recruits of on large (>4 m3) marked boulders from July 2008 to February 2009 at Due Sorelle (black) and La Vela (purple).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2875393&req=5

pone-0010791-g005: Natural changes in density of recruits:Average densities (±1 SE, n = 15, 5 sub-quadrats of 6×6 cm from each of 3 plots of 30×30 cm) of C. barbata recruits of on large (>4 m3) marked boulders from July 2008 to February 2009 at Due Sorelle (black) and La Vela (purple).
Mentions: We found virtually no recruits neither underneath canopies of Cystoseira nor in any other of the dominant habitats comprising mussel beds, stands of simpler seaweeds, or mixed mosaics of the two. In all these habitats recruits, if any, occurred only very sporadically (<1 recruits per 2.5 m2). However, at both sites we found occasional patches of extremely dense recruits of Cystoseira, reaching up to >90% cover (Fig. 4) and densities as high as 16 juveniles per 6×6 cm sub-quadrat (Fig. 5). These patches of recruits were mainly confined to shallow boulders otherwise generally covered by thin filamentous turfs or other small ephemeral algae. On average, cover and density of recruits were highest at Due Sorelle (significant effect of factor Site for cover, F1,8 = 15.97, P<0.01), and based on our transects we estimated they accounted for 5 to 8% of the surveyed area at La Vela and Due Sorelle, respectively (Fig. 2a).

Bottom Line: Lack of surrounding adult canopies did not seem to impair the potential for assisted recovery, suggesting that in these systems recovery could be actively enhanced even following severe depletions.Moreover, we demonstrate that the mere restoration of environmental conditions preceding a loss, if possible, may be insufficient for ecosystem restoration, and is scarcely cost-effective.We conclude that the loss of complex marine habitats in human-dominated landscapes could be mitigated with appropriate consideration and management of incremental habitat changes and of attributes facilitating system recovery.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Biologia Evoluzionistica Sperimentale and Centro Interdipartimentale di Ricerca per le Scienze Ambientali, University of Bologna, Ravenna, Italy. sperkol@gmail.com

ABSTRACT

Background: Predicting and abating the loss of natural habitats present a huge challenge in science, conservation and management. Algal forests are globally threatened by loss and severe recruitment failure, but our understanding of resilience in these systems and its potential disruption by anthropogenic factors lags well behind other habitats. We tested hypotheses regarding triggers for decline and recovery potential in subtidal forests of canopy-forming algae of the genus Cystoseira.

Methodology/principal findings: By using a combination of historical data, and quantitative in situ observations of natural recruitment patterns we suggest that recent declines of forests along the coasts of the north Adriatic Sea were triggered by increasing cumulative impacts of natural- and human-induced habitat instability along with several extreme storm events. Clearing and transplantation experiments subsequently demonstrated that at such advanced stages of ecosystem degradation, increased substratum stability would be essential but not sufficient to reverse the loss, and that for recovery to occur removal of the new dominant space occupiers (i.e., opportunistic species including turf algae and mussels) would be required. Lack of surrounding adult canopies did not seem to impair the potential for assisted recovery, suggesting that in these systems recovery could be actively enhanced even following severe depletions.

Conclusions/significance: We demonstrate that sudden habitat loss can be facilitated by long term changes in the biotic and abiotic conditions in the system, that erode the ability of natural ecosystems to absorb and recover from multiple stressors of natural and human origin. Moreover, we demonstrate that the mere restoration of environmental conditions preceding a loss, if possible, may be insufficient for ecosystem restoration, and is scarcely cost-effective. We conclude that the loss of complex marine habitats in human-dominated landscapes could be mitigated with appropriate consideration and management of incremental habitat changes and of attributes facilitating system recovery.

Show MeSH