A preliminary evaluation of shallow-water rhodolith beds in Bahia Magdalena, Mexico

Abstract

<jats:p>The aim of the present study was to describe the structure of shallow-water rhodolith beds from Bahia Magdalena, one of the most productive estuarine systems of the Mexican Pacific coasts. From September 2008 to May 2009 four rhodolith beds were found (between 1 and 3 m depth) and population descriptors such as rhodolith density, size classes, branch density, volume and weight were determined. The dominant rhodolith forming species was Lithophyllum margaritae. The size of beds ranged from 7,600 to 17,800 m2 approximately with densities from 42.2 to 215.9 ind.m-2. In these beds, L. margaritae shows fruticose and foliose growth forms, from which spherical forms were predominant (81-99%). Branch density (from 3.0 to 13.3 branches.cm-2) varied significantly (p &lt; 0.05) among beds. The average volume (from 2.0 to 400 mL) and wet weight (from 32.4 to 84.8 g) was not significantly different among sites, but a significant positive correlation (r = 0.95, p &lt; 0.05) was found between these parameters. The size of plants ranged from 2.0 to 11.5 cm with predominant size classes of 40.1-60 mm. Differences in rhodolith density, branch density and sphericity were attributed to possible differences in hydrodynamic conditions among sites. These beds were also a suitable habitat for high diversity of associated sponges. A non-metric multidimensional scaling (MDS) analysis using sponge species data revealed variability in the distribution of sponge assemblages among sites, which is likely the result of differences in environmental conditions. Although these rhodolith beds are not as extensive as those of other regions, our preliminary surveys revealed that they are a common habitat in Bahía Magdalena and likely have an important role in the productivity of this estuarine system.</jats:p>

Sponge–rhodolith interactions in a subtropical estuarine system

“…It is important to mention that bed 1 is positioned at the entrance of a relatively narrow channel closer to the mouth of the bay, which may improve the water flow and could make it different in sponge abundance and rhodolith shape compared to the other beds. In accordance with a previous study conducted in four of these beds, a non-metric multidimensional scaling (MDS) analysis using presence/ absence sponge species data revealed variability in the distribution of sponge assemblages among and within sites, which is likely the result of differences in environmental conditions (Á vila and Riosmena-Rodríguez 2011).…”

Sponges from rhodolith beds surrounding Ustica Island marine protected area (southern Tyrrhenian Sea), with a comprehensive inventory of the island sponge fauna

“…This result reveals the considerable diversification of sponge assemblages associated with Mediterranean RBs and is in agreement with previous studies conducted along Mexican coasts (e.g. Ávila and Riosmena-Rodríguez 2011), which recorded a certain variability between sponge assemblages from RBs a few kilometres from each other. In contrast, other studies (e.g.…”

“…On the whole, variability in species diversity and abundance of the associated community across RBs is related to rhodolith complexity and size, which control microhabitat diversification (Grall and Glémarec 1997), but also to other ecological factors associated with larval recruitment and the impact of human activities (Ávila and Riosmena-Rodríguez 2011). In this scenario, the greatest coralline diversity recorded for rhodoliths of temperate regions (Hernandez-Kantun et al 2017), and in particular the much higher values reported for Mediterranean rhodoliths than for those of the northeast Atlantic (Basso et al 2017), are probably responsible for a greater internal diversification of Mediterranean RBs and consequently of the associated communities.…”

Photosynthetic activity estimated as in vivo chlorophyll a fluorescence in calcareous red macroalgae

“…Mercado et al (1998) attributed this result to the higher amount of CO 2 available for the red algae. In the case of the rhodolith populations in Magdalena Bay, the attached epifauna mainly consisted of sponges (Ávila and Riosmena-Rodríguez 2011). Ávila et al (2012) found 13 species of sponges living associated with these non-geniculate macroalgal beds, forming a complex and diverse habitat.…”