Quantitative Estimates of Bio-Remodeling on Coastal Rock Surfaces

Abstract

Abstract:Remodeling of rocky coasts and erosion rates have been widely studied in past years, but not all the involved processes acting over rocks surface have been quantitatively evaluated yet. The first goal of this paper is to revise the different methodologies employed in the quantification of the effect of biotic agents on rocks exposed to coastal morphologic agents, comparing their efficiency. Secondly, we focus on geological methods to assess and quantify bio-remodeling, presenting some case studies in an area of the Mediterranean Sea in which different geological methods, inspired from the revised literature, have been tested in order to provide a quantitative assessment of the effects some biological covers exert over rocky platforms in tidal and supra-tidal environments. In particular, different experimental designs based on Schmidt hammer test results have been applied in order to estimate rock hardness related to different orders of littoral platforms and the bio-erosive/bio-protective role of Chthamalus ssp. and Verrucariaadriatica. All data collected have been analyzed using statistical tests to evaluate the significance of the measures and methodologies. The effectiveness of this approach is analyzed, and its limits are highlighted. In order to overcome the latter, a strategy combining geological and experimental-computational approaches is proposed, potentially capable of revealing novel clues on bio-erosion dynamics. An experimental-computational proposal, to assess the indirect effects of the biofilm coverage of rocky shores, is presented in this paper, focusing on the shear forces exerted during hydration-dehydration cycles. The results of computational modeling can be compared to experimental evidence, from nanoscopic to macroscopic scales.

Spatio-temporal variability in Mediterranean rocky shore microphytobenthos

“…In addition, our results could be explained by the capacity of EMPB to move and shelter within microscopic spaces following an increase in light intensity and/or desiccation stress from the morning until the early afternoon. Although the vertical migration range in rock substrata is apparently limited, rock surfaces are subjected to erosive mechanisms, such as weathering processes and activity of boring organisms (including cyanobacteria), which can create superficial holes or crevices of variable, microscopic size (Golubic 1969, Naylor et al 2012, Pappalardo et al 2016 in this study). These hypotheses were supported by the particularly evident decrease in RVI values on 11 May 2012, when the average air temperature was relatively high, especially compared with the other 2 sampling days.…”

Cool barnacles: Do common biogenic structures enhance or retard rates of deterioration of intertidal rocks and concrete?

“…In doing so, some organic covers are thought to limit wetting-drying cycles, and damaging salt crystallisation and hydration events (e.g., Gowell et al, 2015). In contrast to microorganisms and plants, we are aware of only one published empirical study (Pappalardo et al, 2016) exploring the potential influence of common sedentary marine animals (such as barnacles, mussels and encrusting worms) on rock breakdown in the coastal zone.…”

“…Recently, Pappalardo et al (2016) attempted to quantify the influence of barnacles (C. montaguii and C. stellatus) on rock hardness directly (using a Schmidt Hammer) at a range of field sites in Italy. Their observations show that patterns were inconsistent between sites, and differences were generally inconclusive, or at most very small.…”

Testing A Methodology to Assess Fluctuations of Coastal Rocks Surface Temperature

“…Our temperature record, instead, is strictly related to the temperature of the rock surface. A hypothesis for the interpretation of our evidence, based on data provided by [17,27] may account for a "micro-greenhouse effect" triggered by the barnacle cover. These biota, in fact, produce carbon dioxide through respiration as well as the processes through which the build their shell.…”