Fig 1.
Location of the bathymetric transect (15, 50, 100, and 250 m) south-west of the Peloponnese Peninsula in the Ionian Sea.
Numbers show the locations of light measurements that were carried out in the framework of the European Commission’s Marine Sciences & Technology (MAST) program [38] (S1 Fig). Base map displayed in Ocean Data View [39].
Fig 2.
Photographs of an experimental platform.
(A) Each platform is composed of a 54 x 60 cm PVC frame with four concrete filled PVC tube legs and experimental substrates on the up- and down-facing side. (B) View of the down-facing side of a platform equipped with limestone and PVC plates for the investigation of bioerosion and accretion rates, shells of the Mediterranean bivalve Callista chione for the analysis of bioerosion traces, and a water temperature data logger. Smaller PVC and limestone plates are mounted for the investigation of bacterial biofilms, which are not the scope of the present paper.
Fig 3.
Water temperature measurement during the experiment from March 2008–2009.
Dashed line marks the replacement from summer to winter platforms in October 2008. Due to platform and data loss, no water temperature is available for 15 and 250 m winter exposure, respectively.
Fig 4.
Box plots of bioerosion (A-C), accretion (D-F), and net limestone erosion rates (G-I) in up-facing (u) and down-facing (d) substrates from summer (A, D, G), winter (B, E, H), and one year exposure (C, F, I).
Accretion is given for limestone (white) and PVC substrates (grey).
Table 1.
Results of three-way permutational analysis of variance (PERMANOVA) testing effects of water depth, seasonal exposure, and substrate orientation on bioerosion rates from 50–250 m (statistically significant values are marked in bold).
Table 2.
Results of four-way permutational analysis of variance (PERMANOVA) testing effects of water depth, seasonal exposure, substrate orientation, and substrate type on accretion rates from 50–250 m (statistically significant values are marked in bold).
Table 3.
Results of three-way permutational analysis of variance (PERMANOVA) testing effects of water depth, seasonal exposure, and substrate orientation on net limestone erosion rates from 50–250 m (statistically significant values are marked in bold).
Fig 5.
The inventory of bioerosion traces for the various water depths, substrate orientations (u = up-facing, d = down-facing), and exposure (summer, winter, and one year), categorised by trace types.
Fig 6.
SEM images of epoxy-resin casts taken from Callista shells showing cyanobacterial (A-E) and chlorophyte (F-L) microborings.
(A-B) Fascichnus dactylus, 50 m up, winter and 15 m up, one year, (C) Scolecia filosa, 15 m up, one year, (D) Eurygonum nodosum, 15 m up, one year, (E) Fascichnus frutex, 15 m up, one year, (F-G) Ichnoreticulina elegans, 100 m up, summer and 50 m up, winter, (H) Rhopalia catenata, 15 m up, summer, (I) Rhopalia clavigera, 50 m up, winter, (J) Rhopalia spinosa, 50 m up, winter, (K) Eurygonum pennaforme, 50 up, winter, (L) Fascichnus grandis, 15 m up, one year.
Fig 7.
SEM images of epoxy-resin casts taken from Callista shells showing fungal microborings (A-F) and traces of other organotrophs (G-L).
(A) Flagrichnus baiulus, 50 m down, summer, (B) Flagrichnus profundus, 50 m down, summer, (C) Saccomorpha clava, 250 m up, one year, (D) Saccomorpha sphaerula, 50 m up, winter, (E) Orthogonum fusiferum (arrows mark swellings), 100 m up, one year, (F) Planobola radicatus, 100 m up, winter, (G) Semidendrina pulchra, 50 m down, winter, (H) ‘Super thin form’, 250 m down, winter, (I) Entobia mikra, 15 m up, one year, (J) Entobia nana, 15 m up, one year, (K) Scolecia serrata, 250 m up, winter, (L) ‘Dendroid form 1’, 100 m up, one year.
Fig 8.
Light microscopic (A-B, D, F-G, I) and SEM images (C, E, H) of limestone blocks and Callista shells showing macroborings (A-E), attachment scars (F-H), and grazing traces (I).
(A-B) ‘Foraminiferal Pits’, 15 m up, one year, (C) Entobia isp., 15 m down, one year, (D-E) Talpina isp., 50 m down, winter and summer, (F) Centrichnus eccentricus, 100 m down, summer, (G) Renichnus arcuatus, 15 m up, one year, (H) Ophthalmichnus lyolithon, 100 m up, summer, (I) Gnathichnus pentax, 15 m up, one year.
Fig 9.
SEM images of summer samples of surface and cross-sections showing the degree of bioerosion with water depth and substrate orientation.
(A) 15 m up, (B) 15 m down, (C) 50 m up, (D) 50 m down, (E) 100 m up, (F) 100 m down, (G) 250 m up, and (H) 250 m down.
Fig 10.
SEM images of winter samples of surface and cross-sections showing the degree of bioerosion with water depth and substrate orientation.
(A) 50 m up, (B) 50 m down, (C) 100 m up, (D) 100 m down, (E) 250 m up, and (F) 250 m down.
Fig 11.
SEM images of one year samples of surface and cross-sections showing the degree of bioerosion with water depth and substrate orientation.
(A) 15 m up, (B) 15 m down, (C) 50 m up, (D) 50 m down, (E) 100 m up, (F) 100 m down, (G) 250 m up, and (H) 250 m down.
Fig 12.
Multidimensional scaling plot (MDS) comparing summer, winter, and one year bioerosion traces observed in up- and down-facing substrates in 50–250 m water depth.
Three main clusters (1, 2, 3) and two subclusters (1a, 1b) are separated with a Bray-Curtis-Similarity of 10 and 80, respectively. See S2 Fig for underlying cluster analysis (S = summer, W = winter, O = one year; U = up-facing, D = down-facing).
Table 4.
Results of two-way permutational analysis of similarity (ANOSIM) testing effects of water depth, seasonal exposure, and substrate orientation on bioerosion traces from 50–250 m (statistically significant values are marked in bold).