Hydrography of shellfish harvesting areas in the western Cantabrian coast (Rías Altas, NW Iberian Peninsula)

Abstract

Intertidal shellfish banks in estuarine areas are influenced by a wide variety of environmental conditions, including the physical and chemical characteristic of the water that floods the grounds. In this study we carry out a cross-comparison of the hydrographic characteristics and nutrient fertilization patterns of the waters that laps the shellfish grounds of a group of five drowned valleys collectively known as "Rías Altas", located in the western Cantabrian coast (NW Iberian Peninsula). This region is affected by coastal upwelling from June to August resulting in a water exchange between the embayments and the shelf varying between 31.5 and 220.5 m 3 s −1. The fresh water discharge followed a seasonal cycle too, with maxima in winter and minima in summer, and longterm average flow rates ranging from 5.9 m 3 s −1 to 22.2 m 3 s −1. Significant differences were observed among the five embayments with regard to temperature and salinity and also with inorganic nutrients, chlorophyll a and particulate organic matter concentrations in the continental waters. Highlights: • Continental waters dictate the different fertilisation patterns among the Rías Altas • Extension and geomorphology of the drainage basins explains continental nutrient inputs • Continental nutrient inputs control organic matter concentrations in the inner rías • Production in the inner rías is extremely P-limited

Multivariate substrate characterization: The case of shellfish harvesting areas in the Rías Altas (north‐west Iberian Peninsula)

“…also points to a rather stationary water circulation and nutrient fertilization pattern in these coastal inlets, resulting from the vigorous mixing of a common marine end‐member and a differential continental end‐member for each coastal inlet (Cerdeira‐Arias et al. , 2018) that produce a consistent impact in the sedimentary record.…”

“…The high concentrations of P 2 O 5 indicate the high productivity presented by cluster 2, especially if it is taken into account that phosphate is the limiting nutrient in continental waters in these embayments (Cerdeira‐Arias et al. , 2018).…”

“…These differential characteristics of the waters in the Ría de Ortigueira are mainly related to the distinctive chemical composition of the rivers draining into this coastal inlet (Cerdeira‐Arias et al. , 2018). Concomitantly, for each coastal inlet, sites with more terrestrial influence (higher PC2 scores) were covered by waters with higher levels of chlorophyll.…”

“…In doing so, the first two PCs (see below) were modelled as a function of chlorophyll‐ a and inorganic nitrogen sampled at the high tide in the same sites as the sediments during an annual cycle from April 2008 to March 2009 (see Cerdeira‐Arias et al. , 2018, for further details) using Generalized Additive Models (GAMs) to allow for non‐linearities.…”

“…Sampling sites coincided with the places where the main infaunal bivalve species are harvested (Cerdeira‐Arias et al. , 2018). The resulting characterization will be discussed in the context of the contrasting geology and morphology of these embayments.…”