Central Cantabrian Sea Research Articles

Spatial and seasonal variability of picoplankton abundance and growth rates in the southern Bay of Biscay

Autotrophic and heterotrophic picoplankton play fundamental roles in marine food webs and biogeochemical cycles. However, their growth responses have seldom been jointly assessed, including many temperate regions such as the Bay of Biscay. There, previous studies have shown their relevance in carbon fluxes. We describe here the spatio-temporal variability of the abundances and growth rates of the picoplanktonic groups routinely distinguished by flow cytometry (Synechococcus and Prochlorococcus cyanobacteria, two groups of differently sized picoeukaryotes and two groups of heterotrophic bacteria distinguished by their relative nucleic acid content) in the central Cantabrian Sea (S Bay of Biscay). To that end, from February to December 2021 we collected surface water on 5 occasions from 6 stations distributed along the S Bay of Biscay (6-3°W) and incubated it after removing protistan grazers in order to determine their dynamics along the seasonal cycle as well as the inshore-offshore and the west-east gradients. Seasonal variations in initial and maximum abundances generally matched previous knowledge of the region but growth rates were more variable, with Prochlorococcus and high nucleic acid (HNA) bacteria showing the maximum values (up to 2 d−1) while negative growth was observed in one third of Synechococcus incubations. Temporal differences generally overrode differences along the inshore-offshore gradient in trophic status while in situ and maximum abundances of most of the groups generally decreased towards the east following the increase in stratification and lower nutrient availability. Responses to stratification suggest Prochlorococcus and low nucleic acid (LNA) cells may prevail among autotrophic and heterotrophic bacteria, respectively, in a warmer ocean.

Characterization of marine heatwaves in the Cantabrian Sea, SW Bay of Biscay

The trend towards an increased incidence of marine heatwaves (MHWs) due to climate change poses a serious threat to the health of coastal ecosystems. Here, we characterized MHWs based on daily in situ water temperature measurements collected from 1998 to 2019 in two intertidal coves, Oleiros and La Franca, located in the central Cantabrian Sea coast, N Spain. The two study locations cover the transition zone between cold- and warm-temperate benthic communities that characterizes the biogeography of intertidal assemblages along the SW Bay of Biscay. We examined the incidence, duration and magnitude of MHWs, and assessed the emergence of trends towards more frequent, prolonged and intense MHWs during the study period. We further assessed mechanistic links with modes of climate variability by examining the association between MHW occurrence and the East Atlantic pattern (EA). We detected 78 MHW events between Jan. 1998 and Mar. 2019 (40 in Oleiros, 38 in La Franca) and more than half were synchronous among study locations. The incidence, duration, and intensity of MHWs were higher during the positive phase of the EA, which is associated with air pressures above normal and southwesterly winds during summer. The recorded MHWs also coincided with documented shifts in the abundance and distribution of dominant macroalgae species that triggered abrupt changes in the structure of intertidal communities of the region. Our findings and the present scenario of climate change emphasize the need to enhance research around the trends in the occurrence of MHWs in the coast of northern Spain, and the NE Atlantic Ocean coast in general.

Mapping the habitats of a complex circalittoral rocky shelf in the Cantabrian Sea (south Bay of Biscay)

This work focuses on the study of habitats and communities of a high structural complexity area at different levels and scales. This gives us a better understanding of an area from an ecological point of view and at the same time provides us with tools that will facilitate management measures. It was developed in a complex circalittoral rocky platform of the central Cantabrian Sea (Bay of Biscay). The sampling was carried out using a towed photogrammetric vehicle and a rock dredge, which was used for the identification of the species. The first level of the study was the abiotic characterization of the area and the analysis of the communities. These analysis were developed using the unsupervised k-means classification method. For abiotic characterization we used the variables directly associated with the composition and morphology of the ground, such as backscatter, BPI (Bathymetric Position Index), roughness and slope. Depth was also included to discriminate between the circalittoral and bathyal zones. We obtained 5 different classes, which we related to the ground types observed by photogrammetry. In the analysis of the communities, the cluster was based on the sampling units extracted from the images (∼10 m), from which 5 assemblages were obtained, providing information on the most abundant species of each class supplied by the abiotic study. The second level was carried out considering a management approach and was based on the modeling of the area at lower resolution, more suitable for the analysis of the habitat-fisheries interactions. Thus, the main habitat-forming species (HFS) of the entire circalittoral area were used to perform delta models based on GAMs (Generalize Additive Models). Obtaining the predictions of presence/absence and combining it with the predictions of densities, we got the zero inflated values density-based model. As all the identified habitats have vulnerable benthic species of a certain size settled on rocky bottoms, they can all be considered to belong to the designation 1170 reefs of the Habitats Directive.

Diversity and distribution of bivalve molluscs in the Central Cantabrian Sea and the Avilés Canyons System (Bay of Biscay)

Bivalve molluscs is one of the dominant benthic groups in soft-sediment communities off the Atlantic Ocean, including the European margin and the Bay of Biscay. The current knowledge of deep-sea Euro-Atlantic bivalves and their distribution is still far from comprehensive and has been the scope of several recent publications. We examined the collected bivalve samples from two oceanographic campaigns (COCACE and BIOCANT) carried out in the central Bay of Biscay, including the Avilés Canyons System (ACS), a Site of Community Importance within the Natura 2000 Network. Bivalve specimens were collected from the continental shelf, slope and bathyal zones, ranging in deep from 25 to 4700 m. This is the first study focused on bivalve diversity from the Cantabrian Sea that covers such a wide bathymetric range. Eighty-four live taxa in 36 families were identified; Cetomya neaeroides is reported for the first time in the area. We provide photographs showing the shell diagnostic features of all recorded species. The conducted Multivariate Analysis showed three species assemblages: i) samples from shallow waters (continental shelf); ii) intermediate depths (shelf and upper slope) and iii) deep water (slope and abyssal plain). Depth was the main structuring factor that influenced the distribution of the recorded species and the higher species richness was found on the continental shelf. The feeding strategy and the substrate preference appeared as not significant factors in the zonation patterns of the studied bivalves.

Alongshore upwelling modulates the intensity of marine heatwaves in a temperate coastal sea

Analyses of long-term temperature records based on satellite data have revealed an increase in the frequency and intensity of marine heatwaves (MHWs) in the world oceans, a trend directly associated with global change according to climate model simulations. However, these analyses often target open ocean pelagic systems and rarely include local scale, field temperature records that are more adequate to assess the impact of MHWs close to the land-sea interface. Here, we compared the incidence and characteristics of open ocean MHWs detected by satellites with those observed in the field over two decades (1998–2019) at two temperate intertidal locations in the central Cantabrian Sea, southern Bay of Biscay. Satellite retrievals tended to smooth out cooling events associated with intermittent, alongshore upwelling, especially during summer. These biases propagated to the characterization of MHWs and resulted in an overestimation of their incidence and duration close to the coast. To reconcile satellite and field records, we developed a downscaling approach based on regression modeling that enabled the reconstruction of past temperatures and analyze MHW trends. Despite the cooling effect due to upwelling, the temperature reconstructions revealed a six-fold increase in the incidence of MHWs in the Cantabrian Sea over the last four decades. A comparison between static (no trend) vs. dynamic (featuring a linear warming trend) MHW detection thresholds allowed us to attribute over half of the increase in MHW incidence to the ocean warming trend. Our results highlight the importance of local processes to fully characterize the complexity and impacts of MHWs on marine coastal ecosystems and call for the conservation of climate refugia associated with coastal upwelling to counter the impacts of climate warming.

Recent brachiopod diversity and distribution from the central Cantabrian Sea and the Avilés Canyons System (Bay of Biscay)

An accurate knowledge of the species diversity from deep-sea ecosystems is an imperative requirement in order to protect these environments in the context of global change and the biodiversity loss. We have examined the Brachiopoda samples collected during the COCACE (1987–88) and BIOCANT (2012–13) oceanographic cruises, from the central Cantabrian Sea and the Avilés Canyons System (ACS). The ACS is included in the Natura 2000 as a Site of Community Importance. Brachiopod specimens were collected from the continental shelf, slope and bathyal zones, ranging in deep from 117 to 4700 m. Nine hundred and thirty specimens belonging to 15 taxa (12 species and three subspecific varieties), in 12 families, were recognized. The species Dyscolia subquadrata is reported for the first time in the study area, constituting a new record from the Cantabrian Sea. We provide brief notes about the ecology and distribution of the collected species from the study area. Furthermore, we trace the biogeographical history of the involved species and review their main substrate and bio-depth zone preferences.

Seasonal dynamics of natural Ostreococcus viral infection at the single cell level using VirusFISH.

Ostreococcus is a cosmopolitan marine genus of phytoplankton found in mesotrophic and oligotrophic waters, and the smallest free-living eukaryotes known to date, with a cell diameter close to 1μm. Ostreococcus has been extensively studied as a model system to investigate viral-host dynamics in culture, yet the impact of viruses in naturally occurring populations is largely unknown. Here, we used Virus Fluorescence in situ Hybridization (VirusFISH) to visualize and quantify viral-host dynamics in natural populations of Ostreococcus during a seasonal cycle in the central Cantabrian Sea (Southern Bay of Biscay). Ostreococcus were predominantly found during summer and autumn at surface and 50 m depth, in coastal, mid-shelf and shelf waters, representing up to 21% of the picoeukaryotic communities. Viral infection was only detected in surface waters, and its impact was variable but highest from May to July and November to December, when up to half of the population was infected. Metatranscriptomic data available from the mid-shelf station unveiled that the Ostreococcus population was dominated by the species O. lucimarinus. This work represents a proof of concept that the VirusFISH technique can be used to quantify the impact of viruses on targeted populations of key microbes from complex natural communities.

High Resolution Spatial Distribution for the Hexactinellid Sponges Asconema setubalense and Pheronema carpenteri in the Central Cantabrian Sea

In the present work we focus on the distribution of two species of sponges. One of these is Asconema setubalense, a sponge found in rocky substrate that was sampled with a photogrammetric vehicle through georeferenced images. The other is Pheronema carpenteri, which inhabits soft bottoms and was sampled by beam trawl. For the spatial distribution modeling of both sponges, the geomorphological variables of depth, slope, broad and fine scale bathymetric position index (BPI), aspect, and types of bottoms were used, all with a resolution of 32 m. Additionally, layers of silicates and currents near the bottom were extracted from Copernicus Marine Environment Monitoring Service (CMEMS), with a resolution of ∼4 and ∼9 km, respectively. Due to the low resolution of the layers, it was considered necessary to validate their use by model comparison, where those that included these variables turned out to be more explanatory than the others. The models were developed in a complex continental break of the Central Cantabrian Sea, which comprises several submarine canyons and a seamount (Le Danois Bank). On the one hand, a very high resolution (32 m) spatial distribution model based on A. setubalense presence was developed using the MaxEnt maximum entropy model. On the other, depending on the availability of density data, generalized additive models (GAMs) were developed for P. carpenteri distribution, although in this case the sampler only allowed a maximum resolution of almost 1 Km. For the A. setubalense, the variables that best explained their distribution were ground types and depth, and for P. carpenteri, silicates, slope, northness, and eastward seawater velocity. The final model scores obtained were an AUC of 0.98 for the MaxEnt model, and an R squared of 0.87 for the GAM model.

DNA barcoding-based assessment of the invasive and native non-crustose Codium species in the central Cantabrian Sea, southern Bay of Biscay

Abstract In this work, we identified non-crustose invasive (Codium fragile subsp. fragile) and native Codium spp. (Codium tomentosum and Codium vermilara) in the central Cantabrian Sea using DNA barcoding (tufA and rbcL genes). We designed a new FCOtufA genetic marker for identifying Codium spp. in fresh and herbarium material. The tufA and rbcL sequences revealed three different single haplotypes for each of the species and a lack of intraspecific genetic diversity. The FCOtufA genetic marker revealed one new haplotype of C. fragile within the native region (South Korea), suggesting the possibility of higher genetic diversity in the donor region of this invasive species.

First record of the abyssal bivalve Halicardia flexuosa (Bivalvia: Verticordiidae) in the Bay of Biscay

Abstract The occurrence of the flexed verticord, Halicardia flexuosa (Verrill & S. Smith [in Verrill], 1881), is reported for the first time from the Bay of Biscay (North Iberian Peninsula). This rare bivalve was collected from deep waters (1200 m depth) of the Avilés Canyon Systems (Central Cantabrian Sea). We provide a detailed description and illustration of the species, as well as brief notes on its ecology at the new locality and its global biogeography.

Holothurian (Echinodermata) diversity and distribution in the central Cantabrian Sea and the Avilés Canyon System (Bay of Biscay).

Here we report on the holothurian fauna at the Avilés Canyon System (Natura 2000 Site of Community Importance), central Cantabrian Sea, northern Spain. The samples were collected during several cruises covering the shelf, the continental slope and the abyssal depth. We identified 174 specimens, belonging to 35 species of the seven orders of class Holothuroidea. Depth was the main structuring agent. Multivariate analysis allowed the differentiation of four main assemblages which corresponded to abyssal plain, lower continental slope, upper continental slope, and continental shelf. Depth had a significant effect on holothurian species richness (it increased with depth at an approximate rate of 1.7 species 1000 m-1), which is consistent with previously described global patterns.

High resolution spatial distribution for the hexactinellid sponges Asconema setubalense and Pheronema carpenteri in the Central Cantabrian Sea

High resolution spatial distribution for the hexactinellid sponges Asconema setubalense and Pheronema carpenteri in the Central Cantabrian Sea

DNA barcoding for assessment of exotic molluscs associated with maritime ports in northern Iberia

ABSTRACTPorts are gateways for aquatic invasions. New arrivals from maritime traffic and disturbed environmental conditions can promote the settlement of exotic species. Molluscs fall into the most prevalent group of invasive species and can have a tremendous impact on aquatic ecosystems. Here we have investigated exotic molluscs in three ports with different intensities of maritime traffic in the Cantabrian Sea. DNA barcodes were employed to identify the species using BLASTn and BOLD IDS assignment. Deep morphological analysis using diagnostic criteria confirmed BLAST species assignation based on COI and 16S rRNA genes. Results confirmed the usefulness of DNA barcoding for detecting exotic species that are visually similar to native species. Three exotic bivalves were identified: Ostrea stentina (dwarf oyster), the highly invasive Crassostrea gigas (Pacific oyster) and Xenostrobus securis (pygmy mussel). This is the first record of O. stentina in the Bay of Biscay and the second of X. securis in the Cantabrian Sea. Furthermore, we report on the presence of the cryptogenic mussel Mytilaster minimus in the central Cantabrian Sea. These exotic species might have been overlooked due to their phenotypic similarity with co-occurring oyster and mussel species. This study illustrates how combining morphological and DNA taxonomic analysis can help in port and marina biosecurity surveys.

Holothurian diversity and distribution in the central Cantabrian Sea and the Avilés Canyon Systems (Bay of Biscay)

Holothurian diversity and distribution in the central Cantabrian Sea and the Avilés Canyon Systems (Bay of Biscay)

Two Streptomyces species producing antibiotic, antitumor, and anti-inflammatory compounds are widespread among intertidal macroalgae and deep-sea coral reef invertebrates from the central Cantabrian Sea.

Streptomycetes are widely distributed in the marine environment, although only a few studies on their associations to algae and coral ecosystems have been reported. Using a culture-dependent approach, we have isolated antibiotic-active Streptomyces species associated to diverse intertidal marine macroalgae (Phyllum Heterokontophyta, Rhodophyta, and Chlorophyta), from the central Cantabrian Sea. Two strains, with diverse antibiotic and cytotoxic activities, were found to inhabit these coastal environments, being widespread and persistent over a 3-year observation time frame. Based on 16S rRNA sequence analysis, the strains were identified as Streptomyces cyaneofuscatus M-27 and Streptomyces carnosus M-40. Similar isolates to these two strains were also associated to corals and other invertebrates from deep-sea coral reef ecosystem (Phyllum Cnidaria, Echinodermata, Arthropoda, Sipuncula, and Anelida) living up to 4.700-m depth in the submarine Avilés Canyon, thus revealing their barotolerant feature. These two strains were also found to colonize terrestrial lichens and have been repeatedly isolated from precipitations from tropospheric clouds. Compounds with antibiotic and cytotoxic activities produced by these strains were identified by high-performance liquid chromatography (HPLC) and database comparison. Antitumor compounds with antibacterial activities and members of the anthracycline family (daunomycin, cosmomycin B, galtamycin B), antifungals (maltophilins), anti-inflamatory molecules also with antituberculosis properties (lobophorins) were identified in this work. Many other compounds produced by the studied strains still remain unidentified, suggesting that Streptomyces associated to algae and coral ecosystems might represent an underexplored promising source for pharmaceutical drug discovery.

Temporal and spatial variability of river plumes in the NW and N Iberian shelf (1987–2007)

The analysis of the salinity gradient estimated from in situ data was applied to characterize the spatial and temporal variability of low density buoyant structures in the North Iberian Shelf (NIS) (i.e. Galicia and Cantabrian Sea). To this aim, we have used salinity data acquired in 20 cruises carried out in spring (around April) between 1987 and 2007 and in 5 across-shelf sections sampled monthly between 1994 and 2005 in the studied area. The time series of the salinity gradient from the across-shelf sections data highlighted the seasonal pattern of occurrence of river plumes. This pattern, mainly related with the seasonality of the precipitation rate, varied along the NIS: high probability of occurrence (>70%) took place between November and February in the Central Cantabrian Sea, while it extended to March in the western and to May in the eastern parts of the studied area. The analysis of the spatial distribution of river plumes during spring pointed out two areas, off Miño and Adour river mouths, where the probability of occurrence of river plumes was high during this period. The presence of plumes in the Central Cantabrian Sea was more sporadic and localized preferentially in the proximity of Nalón and Pas-Besaya river mouths. The time series of plume descriptors, such as the area affected by plumes at 10m depth (AP10, km2) and the mean depth of the plume (zP), differed along the NIS. In the westernmost part, AP10 and zP were significantly lower between 1987 and 1996 than between 1997 and 2006. In the Cantabrian Sea, the values of these descriptors were lower in the central than in the eastern part, and in the latter of these zones the values kept persistently moderate/high during whole period. Plume descriptors were correlated with precipitations and river discharges of the previous month (lag k=1, March) and, in some cases, with the winter values of these forcing factors (k between 5 and 3, November and January respectively).

Photoacclimation of picophytoplankton in the central Cantabrian Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 493:43-56 (2013) - DOI: https://doi.org/10.3354/meps10549 Photoacclimation of picophytoplankton in the central Cantabrian Sea Evaristo Vázquez-Domínguez*, Xosé Anxelu G. Morán, Angel López-Urrutia Spanish Institute of Oceanography (IEO), Oceanographic Center of Xixón, Camín de L’Arbeyal, s/n, 33212 Xixón, Asturies, Spain *Email: ristovazquez@gmail.com ABSTRACT: Photoacclimation of picophytoplankton was studied in the mixed layer of 3 stations in the central Cantabrian Sea (southern Bay of Biscay). Picophytoplankton chl a:carbon ratios (θ) presented minimum values during summer, when irradiance, temperature, and biomass of prokaryotes reached maximum values and inorganic nutrient concentrations were low. Conversely, the maximum θ were reached during winter, coincident with lowest annual irradiance but maximum concentration of inorganic nutrients and higher relative biomass of eukaryotes. Changes in θ were modeled using irradiance as an independent variable. Exponentially decreasing functions of θ with irradiance were significant only when the mean temperatures in the mixed layer were above 14°C. These functions presented light-saturated minimum ratios (θmin) that decreased linearly with temperature and low-light maximum ratios (θmax) that increased exponentially with temperature. Such relationships were used to establish an empirical model that reproduced the seasonality of picophytoplankton θ in the mixed layer, with minima in summer and maxima in winter. A maximum potential θ, θN,T-max, was determined to estimate picophytoplankton growth rates in the central Cantabrian Sea. Combinations of picophytoplankton growth rates and biomass in the mixed layer were used to estimate areal picophytoplankton primary production rates in the euphotic zone that presented a bimodal seasonal cycle, with maxima in late winter (ca. 100 mg C m-2 d-1) and in late autumn (>200 mg C m-2 d-1) and mean annual values around 120 mg C m-2 d-1. KEY WORDS: Light · Temperature · Nutrients · Picophytoplankton · Chl a:carbon ratio · Modeling Full text in pdf format PreviousNextCite this article as: Vázquez-Domínguez E, Morán XAG, López-Urrutia A (2013) Photoacclimation of picophytoplankton in the central Cantabrian Sea. Mar Ecol Prog Ser 493:43-56. https://doi.org/10.3354/meps10549 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 493. Online publication date: November 20, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Trawling disturbance on the isotopic signature of a structure-building species, the sea urchin Gracilechinus acutus (Lamarck, 1816)

Bottom trawling is one of the main sources of anthropogenic disturbance in benthic habitats with important direct and indirect effects on the ecosystem functional diversity. In this study, the effect of this impact on a structure-building species, the sea urchin Gracilechinus acutus, was studied in the Central Cantabrian Sea (southern Bay of Biscay) comparing its isotopic signature and additional population descriptors across different trawling pressures. Trawling disturbance had a significant effect on the studied descriptors. In trawling areas, this urchin showed significantly lower values of biomass and mean size and significantly higher values of fullness index. Moreover, the trawling disturbance effect was also significant in the isotopic signature of G. acutus. Urchins inhabiting untrawled areas showed significant lower values of δ15N than urchins dwelling areas under trawling pressure. The urchins’ isotopic enrichment increased along the species ontogeny regardless of the trawling effort level. Stable isotope analyses are a suitable tool to detect trawling disturbance on the trophic pathways but do not suffice to explain these changes, especially if there is a lack of baseline information.

Circulation patterns at Le Danois Bank, an elongated shelf-adjacent seamount in the Bay of Biscay

Le Danois Bank is a seamount-like topographical feature located at the continental shelf in the central Cantabrian Sea (Bay of Biscay), recently declared Marine Protected Area. The bank is partially connected to the shelf by a saddle, topographically bounding an inner valley. Hydrographical cruises and direct current measurements from current meters, vessel-mounted ADCP and subsurface floats are analysed to describe the main circulation patterns in the area. Records are consistent with the presence of anticyclonic flow at the seamount summit. The inner valley seems to support the development of retentive flow structures and the whole system is affected by strong and variable along-slope currents, thus complicating the overall picture. Scaling arguments, based on non-dimensional parameters accounting for the surrounding flow characteristics and the geometry of the seamount, allow an estimate of the dynamical processes that may be active at the bank. Temporary Taylor cap formation by weak impinging flow may occur, although a clear signature of this feature does not emerge from the observed density fields. The strong local amplification of the diurnal tide suggests the presence of resonant seamount trapped waves. The strength of the semidiurnal tide M 2 in the region, in combination with the steepness of the flanks of the bank, points to a significant contribution of tidally rectified flow to the observed residual anticyclonic flow. An observation of an isopycnal vertically repositioned by 50 m within one downcast/upcast period of a CTD profile indicates the importance of high frequency internal wave dynamics.

Composition and daytime vertical distribution of the ichthyoplankton assemblage in the Central Cantabrian Sea shelf, during summer: An Eulerian study

During summer, wind driven coastal upwelling dominates in the Central Cantabrian Sea (southern Bay of Biscay). Nevertheless, atmospheric forcing is highly variable and wind pulses may cause noticeable and fast hydrographic responses in the shelf region. In this paper, the composition and vertical distribution of the summer ichthyoplankton assemblage during the daytime at a fixed station, located on the Central Cantabrian Sea shelf, are documented. Also, the impact of a short-time scale hydrographic event on the abundance and structure of the larval fish assemblage is examined. Significant small-scale temporal hydrographic variability was observed. Currents showed changes in speed and direction and significant changes in thermocline depth were also observed. A total of 34 taxa of fish larvae were identified. Engraulis encrasicolus eggs and larvae of the shelf-dwelling species Trachurus trachurus, Capros aper and E. encrasicolus dominated the ichthyoplankton assemblage. The distribution of E. encrasicolus eggs and fish larvae was vertically structured. E. encrasicolus egg concentration increased exponentially towards the surface. Fish larvae showed a subsurface peak of concentration and their vertical distribution was not conditioned by thermocline depths. The short term hydrographic event did not affect the vertical distribution of fish larvae but it accounted for significant temporal changes in larval fish assemblage structure and abundance. Results suggest that temperature and light intensity are important factors in the vertical distribution of fish larvae. They also indicate that the temporal monitoring of the larval fish assemblage in this region requires multiple sampling sites.