Responses of marine benthic microalgae to elevated CO<inf>2</inf>

Increasing anthropogenic CO2 emissions to the atmosphere are causing a rise in pCO2 concentrations in the ocean surface and lowering pH. To predict the effects of these changes, we need to improve our understanding of the responses of marine primary producers since these drive biogeochemical cycles and profoundly affect the structure and function of benthic habitats. The effects of increasing CO2 levels on the colonisation of artificial substrata by microalgal assemblages (periphyton) were examined across a CO2 gradient off the volcanic island of Vulcano (NE Sicily). We show that periphyton communities altered significantly as CO2 concentrations increased. CO2 enrichment caused significant increases in chlorophyll a concentrations and in diatom abundance although we did not detect any changes in cyanobacteria. SEM analysis revealed major shifts in diatom assemblage composition as CO2 levels increased. The responses of benthic microalgae to rising anthropogenic CO2 emissions are likely to have significant ecological ramifications for coastal systems. © 2011 Springer-Verlag

Loss and Recovery Potential of Marine Habitats: An Experimental Study of Factors Maintaining Resilience in Subtidal Algal Forests at the Adriatic Sea

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

Multiple Criteria Decision Analysis to Assess Urban and Territorial Transformations: Insights from Practical Applications

This chapter aims at providing concrete reflections about the use of the Multiple Criteria Decision Analysis (MCDAs) in urban and territorial decision processes. The reflections provided by this chapter come from a critical analysis of different case studies faced by the Turin research group (Politecnico di Torino, InterUniversity Department DIST) composed by the authors, in some case in collaboration with other academics. Over the last decade in fact, the authors applied a number of MCDA to case studies of different nature in order to provide answers to decision-making problems in urban and territorial planning realms, towards a sustainable development. Specifically, the case studies analysed in this chapter refer to seven contexts: (i) infrastructural transport planning strategies; (ii) location of undesirable facilities; (iii) strategic urban planning; (iv) urban energy retrofitting; (v) real estate investments; (vi) cultural adaptive reuse of abandoned buildings; and (vii) environmental systems. The aforementioned case studies cover different geographical scales of intervention (local, national and transnational) offering here the opportunity to reflect around the use of MCDA as Analytic Network Process (ANP), ANP and Spatial Decision Support Systems (SDSS), Dominance Based Rough-Sets Approach (DRSA), Measuring Attractiveness by a Categorical Based Evaluation Technique (MACBETH), Preference Ranking Organization METHod for Enrichment of Evaluations (PROMETHEE), CATegorization by Similarity-Dissimilarity (CAT-SD) and Elimination Et Choix Traduisant La Realité (ELECTRE). The applications presented show that the MCDA can be a useful support to the decision-makers in order to structure the decision process in exam, characterized by a plurality of stakeholders with different interests, powers and goals. In particular, starting from the case studies, the authors highlight the applicability and the decision-making relevance of the different MCD