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Mapping microhabitat thermal patterns in artificial breakwaters: Alteration of intertidal biodiversity by higher rock temperature - PubMed

  • ️Tue Jan 01 2019

. 2019 Nov 4;9(22):12915-12927.

doi: 10.1002/ece3.5776. eCollection 2019 Nov.

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Mapping microhabitat thermal patterns in artificial breakwaters: Alteration of intertidal biodiversity by higher rock temperature

Moisés A Aguilera et al. Ecol Evol. 2019.

Abstract

Urbanization is altering community structure and functioning in marine ecosystems, but knowledge about the mechanisms driving loss of species diversity is still limited. Here, we examine rock thermal patterns in artificial breakwaters and test whether they have higher and spatially less variable rock temperature than natural adjacent habitats, which corresponds with lower biodiversity patterns. We estimated rock temperatures at mid-high intertidal using infrared thermography during mid-day in summer, in both artificial (Rip-raps) and natural (boulder fields) habitats. We also conducted diurnal thermal surveys (every 4 hr) in four seasons at one study site. Concurrent sampling of air and seawater temperature, wind velocity, and topographic structure of habitats were considered to explore their influence on rock temperature. Rock temperature was in average 3.7°C higher in the artificial breakwater in two of the three study sites, while air temperature was about 1.5-4°C higher at this habitat at summer. Thermal patterns were more homogeneous across the artificial habitat. Lower species abundance and richness in the artificial breakwaters were associated with higher rock temperature. Mechanism underlying enhanced substrate temperature in the artificial structures seems related to their lower small-scale spatial heterogeneity. Our study thus highlighted that higher rock temperature in artificial breakwaters can contribute to loss of biodiversity and that integrated artificial structures may alter coastal urban microclimates, a matter that should be considered in the spatial planning of urban coastal ecosystems.

Keywords: artificial breakwaters; boulder fields; coastal microclimate; rocky intertidal; thermal patterns; urbanization.

© 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1

Study sites. Location of the different study sites and habitats in Coquimbo (29°S) and Iquique (20°S), and small town (Caleta Hornos, CH) located close to Coquimbo city (~40 km from the La Herradura Bay). Right panel show the specific location of artificial breakwaters (red) and natural habitats (blue) considered in the study. Sites located in Iquique (20°S) were only considered for the substrate thermal pattern surveys

Figure 2
Figure 2

Box plot of (a) the substrate (ST), (b) air (Air T) and (c) seawater temperature, and (d) wind velocity, estimated in rip‐raps (Artificial) and boulder field (Natural) at the different sites considered. The black line in each box is the median, the boxes define the hinge (25, 75% quartile, and the line is 1.5 times the hinge). Points outside the interval (outliers) are represented as dots

Figure 3
Figure 3

Box plot of (a) the rock or substrate temperature (ST) recorded at the different habitats across localities, and (b) substrate temperature and (c) coefficient of variation (CV) recorded at the different positions on the rip‐raps and natural boulders. Insert in A shows a box plot with the total average rock temperature recorded for the artificial and natural habitat in all localities considered in Coquimbo (30°S). The black line in each box is the median, the boxes define the hinge (25% and 75% quartile, and the line is 1.5 times the hinge). Points outside the interval (outliers) are represented as dots. Sites in (a) correspond to artificial breakwaters (CH_a, CMP, UCN) and corresponding natural boulder fields (CH_n, PG, PP) considered in the “artificial–natural” habitat comparisons

Figure 4
Figure 4

Differences in substrate temperature (°C) between the artificial (AR) and the natural habitat (NA) for the different sites considered (CHn, PG, PP, EPIn, and CAVn correspond to the natural habitats, CHa, CMP, UCN, EPIa and CAVa are the artificial breakwaters considered at the different localities). Bars are 95% confidence intervals estimated through a bootstrapping procedure. Positive values show net increase in substrate temperature in the artificial habitat compared with the natural one. Red diamond and triangle are sites located in Iquique, at northern Chile (20°S)

Figure 5
Figure 5

Substrate and air temperatures recorded during daytime sampling (n = 37 estimations per hour per habitat in each season). (a) Maximum averaged (4‐seasons) substrate temperature recorded at different hours in both the artificial and the natural habitats, (b) boxplot of the maximum substrate temperature recorded at afternoon and evening (16:00–20:00 hr) in summer, (c) average (4‐seasons) air temperature recorded at different hours in both the artificial and the natural habitats (0.5–1.5 m above the substrata), and (d) boxplot of the air temperature recorded at afternoon and evening (16:00–20:00 hr) in summer. The line in each box is the median, the boxes define the hinge (25% and 75% quartile, and the line is 1.5 times the hinge). Points outside the interval (outliers) are represented as dots

Figure 6
Figure 6

Biotic variables recorded in natural and artificial habitats. (a) Box plot of the density of mobile species (n = 64 quadrats per habitat), (b) percent cover of sessile invertebrates and algae, and (c) total species richness (number of species) recorded at the different quadrats located in different positions within the natural and the artificial habitats

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