38th European Marine Biology Symposium, Aveiro (Portugal), 8-12 September 200

Bernárdez Martí, Cristina

Corgos López-Prado, Antonio

Freire, Juan

García Calvo, Beatriz

Godínez Domínguez, Enrique

Pallas Lozano, Alicia

Sampedro Pastor, María Paz

Repositorio da Universidade da Coruña

 138th European Marine Biology Symposium. 8-12 September 2003. Universidade de Aveiro. Portugal  Habitat diversity and postlarval benthic decapod crustacean assemblages in shallow waters of the Ría de A Coruña (NW Spain)  Pallas, A., García-Calvo, B., Corgos, A., Freire, J., Godínez-Domínguez, E., Bernárdez, C. & Sampedro, P.1  Departamento de Bioloxía Animal, Bioloxía Vexetal e Ecoloxía, Universidade da Coruña, Campus da Zapateira s/n, E-15071 A Coruña, Spain 1 Instituto Español de Oceanografía, Centro Oceanográfico de A Coruña, A Coruña Spain  INTRODUCTION  Distribution and abundance of postlarval phases of coastal benthic decapod crustaceans is related to multiple processes affecting both planktonic (larval supply and differential settlement) and benthic (differential mortality, habitat selection and denso-dependence) stages. The high diversity of decapod assemblages in coastal ecosystems results from the interaction between the above processes and the existing high environmental variability and habitat diversity. This study is an attempt to characterize patterns of habitat use and distribution of juvenile and adult stages of benthic postlarval decapod species in shallow bottoms, identifying the main environmental variables affecting these patterns. The comparative capacity of different habitats to support juvenile and adult diversity was also characterized.  SAMPLING  A stratified random survey was carried out along the coast of the Ria de A Coruña (Galicia, NW Spain) during the months of July and August 1998, using a suction sampler operated by divers. Three sampling sites along the main axis of the Ria were selected to identify the meso-scale variability and an array of sampling locations were defined within each site according to the combination of three micro-scale variables: wave exposure, depth and habitat type. Four replicates were taken in each location.  - Wave exposure:  Exposed Sheltered  - Depth: 0: Intertidal 1: 3-5 m 2: 8-12 m  - Habitat type: Sandy bottoms Rocky bottoms: Flat rock surfaces covered with algae Cobble and boulder pools Kelp (Saccorhiza polyschides) holdfasts     ANALYSIS.  Generalized linear models (GLM) were employed to determine the weighted effect of the environmental conditions over the spatial patterns of the postlarval community. The best subsets procedure using the Akaike Information Criterion (AIC) was used to select the best model, and a normal log model was assumed.  Null models were employed to extract common diversity patterns among variable combinations. Individual-based rarefaction curves (Gotelli and Graves, 1996), which generate comparative estimates of species number independently of the 1 KMCANABALCANIDEPORTOCOBOSPAIN43ºN42º8º W 7º50 kmPORTUGALRía de A Coruña 2differences between sample size of the groups compared, were employed as a richness index. The probability of an interspecific encounter PIE (Hurlbert, 1971) was used as an evenness measure. The abundance levels for simulation were fixed according to the sample with lowest abundance to allow the comparison among samples. Both evenness and rarefaction were estimated using EcoSim software (Gotelli and Entsminger, 2001), which uses a Monte Carlo procedure, and 1000 replicate simulations were performed for each estimate.   RESULTS  Shallow bottoms of the Ria de A Coruña show a wide diversity of habitats and support a highly abundant and diverse community of decapods. Our results support the hypothesis that these areas constitute essential nursery habitats for benthic species.  A lower specific diversity was found for adults than for juveniles in nearly all cases (Fig. 1). This difference was more pronounced in Canabal (the most external sampling site). Evenness values for both stages were high (Average PIE > 0.65) in most sampling locations (Table 1). The most internal site (Portocobo) presented a higher homogeneity in richness and evenness values for adults than for juveniles.      Fig. 1. Rarefaction diversity curves. The Y axis represents the expected richness for a given sample size (no. of individuals)  Table 1. Evenness values HABITATAverage PIE Variance PIE Average PIE Variance PIESandy 0,021 0,00026Holdfasts 0,566 0,00046 0,715 0Cobbles 0,451 0,00184 0,836 0,00005Rock surfaces 0,858 0,00014 0,716 0,0007Holdfasts 0,790 0,00023 0,774 0Cobbles 0,739 0,00094 0,667 0,00106Rock surfaces 0,856 0,00024 0,741 0,00048Holdfasts 0,860 0,00008 0,844 0Cobbles 0,861 0,00026 0,851 0,00006Rock surfaces 0,902 0,00009 0,815 0,0001DEPTHAverage PIE Variance PIE Average PIE Variance PIE Depth 0 0,525 0,00137 0,762 0,00026 Depth 1 0,839 0,00018 0,689 0,00044 Depth 2 0,206 0,00155 0,693 0 Depth 0 0,861 0,0002 0,859 0 Depth 1 0,795 0,0007 0,690 0,00086 Depth 2 0,760 0,00069 0,664 0,00036 Depth 0 0,870 0,00016 0,853 0 Depth 1 0,886 0,00017 0,816 0,00023 Depth 2 0,870 0,00021 0,805 0,00021Abund. levelPortocoboCanideCanabal143138148Juveniles Adultos118169137Abund. levelJuveniles Adultos 051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150 170051015202510 30 50 70 90 110 130 150 170051015202510 30 50 70 90 110 130051015202510 30 50 70 90 110 130051015202510 30 50 70 90 110051015202510 30 50 70 90 110Sandy Holdfasts Cobbles Rock surfaces 10 m0 5 HABITAT Juveniles                                              Adults DEPTHJuveniles                                              Adults Portocobo     Canide     Canabal  3The most abundant species occurred in higher density for juvenile over adult stages in most cases (Fig. 2).  All adults belonged to species also found for juveniles. Three main patterns of juvenile and adult distribution were identified: species without adult presence in the sampled area, such as Galathea strigosa; species that remain in the same area, but with observable ontogenic habitat shifts, which is the case of Eualus occultus and species that keep similar habitat use patterns along the life cycle, e.g. Pisidia longicornis.    Fig. 2. Densities of juveniles and adults of the most abundant species in different sites, exposure levels, depths and habitats   Although all the tested variables showed an important effect on the distribution of decapod species, variability in spatial patterns is mainly due to habitat type, which is a micro-scale operating factor. Meso-scale variability related to sites along the Ria, as well as other micro-scale factors, i.e. depth and wave exposure, have a lower effect on spatial distribution of post-recruits.  A similar pattern in the composition of parameters included in the most parsimonious models (GLM) was found between juveniles and adults on rocky bottoms (Table 2).  In both cases habitat type was the most frequent variable in models for the most abundant species (87.5% for juveniles; 64.3% for adults), while wave exposure shows the lowest percentage of occurrence in models for both juveniles (56.2%) and adults (50%).   The GLM results for kelp holdfast samples showed a lower effect of all the factors on juvenile and adult patterns, with no observable differences among variables. A high proportion of the models obtained for this group of samples were not significant. This suggests that the influence of environmental conditions could be attenuated inside kelp holdfasts. These results, altogether with the ontogenic distribution patterns of the species found in holdfasts as well as the significant differences observed in diversity between them and rocky habitats, suggest that holdfasts are used as a temporary shelter rather than a nursery habitat.  Sandy bottom coverage was significant only in sheltered areas of one sampling site and therefore GLM was not fitted. The diversity and evenness found in this habitat were very low due to the dominance of the Paguridea. Early juveniles of this group showed an average density of 427 Ind/m2 (Fig. 3), reaching 1227 Ind/m2 at 10 m deep. Data found support the hypothesis that these bottoms are essential recruitment habitats for this group.    Rocky BottomsPisidialongicornisAthanasnitescensThoraluscranchiiHippolytevariansPilumnusspp.ProcessaedulisXantho spp.PirimeladenticulataPorcellanaplatychelesPalaemonspp.GalatheastrigosaEualusoccultusKelp Holdfasts100500501005005010060402002040200204020020406050510201001020305051050510150510150246842024420241050510156420264202420240,20,00,20,40,60,40,20,00,20,00,20,40,60,000,040,080,120,00,10,20123PortocoboCanideCanabalExposedShelteredDepth 0Depth1Depth 2HoldfastsNo. Ind/ holdfast JuvenilesAdultsPortocoboCanideCanabalExposedShelteredDepth 0Depth1Depth 2CobblesJuvenilesAdultsRocksurfacesNo. Ind/ m2No. Ind/ holdfastNo. Ind/ holdfastNo. Ind/ m2 4Table 2. GLM models for rocky bottoms and kelp holdfasts  J A J A J A J A J A J A J A J A J A J A J A J A J APaguridea 5 3 580,69 599,02 ** ** 2 2 219,33 169,74 ** 0,06Pisidia longicornis 6 6 761,47 746,53 ** ** 4 3 158,72 181,19 ** **Athanas nitescens 3 5 853,99 36,03 ** 0,03 3 3 346,98 263,11 0,05 **Thoralus cranchii 3 4 557,14 664,91 ** ** 3 4 147,21 228,30 ** **Hippolyte varians 5 3 591,01 471,58 ** ** 2 2 206,39 199,48 0,23 0,02Pilumnus hirtellus 4 6 558,43 222,04 ** ** 2 4 221,59 139,13 0,08 0,02Pilumnus spinifer 4 4 448,60 292,23 ** ** 4 2 119,22 77,20 ** **Processa edulis 4 1 438,12 134,11 0,02 0,36 1 1 94,67 -47,64 0,07 0,31Xantho pilipes 6 5 416,78 292,35 ** ** 1 -47,64 0,31Xantho incisus 5 3 350,50 296,99 ** ** 1 1 -47,64 70,22 0,31 0,08Hippolyte sp. 1 1 318,66 182,25 0,12 0,29 1 2 93,91 -11,34 0,82 **Pirimela denticulata 6 2 424,29 103,93 ** 0,02 2 78,77 0,04Porcellana platycheles 3 3 442,98 150,48 ** ** 1 -16,51 0,14Palaemon longirostris 5 594,87 ** 2 -16,74 0,11Galathea strigosa 6 348,89 ** 2 164,14 **Eualus occultus 5 2 264,77 266,42 ** 0,05Percentage 87,5 64,3 75,0 57,1 75,0 57,1 56,2 50,0 ** p < 0,01 42,9 36,4 42,9 54,5 42,9 45,5 ** p < 0,01 Variable included  Variable included  Variable not included  Species not present in model (juveniles)  in model (adults)  in modelSampling siteHabitat Sampling site Depth Exposure pROCKY BOTTOMS KELP HOLDFASTSDepth Exposure Degrees of Freedom AICDegrees of Freedom AIC p    Fig. 3. Densities of juveniles and adults of the group Paguridea in different sites, exposure levels, depths and habitats   LITERATURE CITED.  Gotelli, N.J. & Graves GR (1996) Null models in ecology. Smithsonian Institution Press. Washington  Hurlbert, S.M. (1971) The non-concept of species diversity, A critique and alternative parameters. Ecology 52: 577-586  Gotelli, N.J. & Entsminger, G.L. (2001). EcoSim: Null models software for ecology. Version 7.0. Acquired Intelligence Inc. & Kesey-Bear. http://homepages.together.net/~gentsmin/ecosim.htm    CanideCanabalDepth 0Depth 1Depth 2CobblesJuvenilesAdultsNo. Ind/ m2Sandy50050100150200250300350400450No. Ind/ m2

Habitat diversity and postlarval benthic decapod crustacean assemblages in shallow
waters of the Ría de A Coruña (NW Spain)

Habitat diversity and postlarval benthic decapod crustacean assemblages in shallow waters of the Ría de A Coruña (NW Spain)Pallas, A., García-Calvo, B., Corgos, A., Freire, J., Godínez-Domínguez, E., Bernárdez, C. & Sampedro, P.1Departamento de Bioloxía Animal, Bioloxía Vexetal e Ecoloxía, Universidade da Coruña, Campus da Zapateira s/n, E-15071 A Coruña, Spain1 Instituto Español de Oceanografía, Centro Oceanográfico de A Coruña, A Coruña Spain38th European Marine Biology Symposium. 8-12 September 2003. Universidade de Aveiro. Aveiro, PortugalINTRODUCTION. Distribution and abundance of postlarval phases of coastal benthic decapod crustaceans is related to multiple processes affecting both planktonic (larval supply and differential settlement) and benthic (differential mortality, habitat selection and denso-dependence) stages. The high diversity of decapodassemblages in coastal ecosystems results from the interaction between the above processes and the existing high environmental variability and habitat diversity. This study is an attempt to characterize patterns of habitat use and distribution of juvenile and adult stages of benthic postlarval decapod species in shallow bottoms, identifying the main environmental variables affecting these patterns. The comparative capacity of different habitats to support juvenile and adult diversity was also characterized.J A J A J A J A J A J A J A J A J A J A J A J A J APaguridea 5 3 580,69 599,02 ** ** 2 2 219,33 169,74 ** 0,06Pisidia longicornis 6 6 761,47 746,53 ** ** 4 3 158,72 181,19 ** **Athanas nitescens 3 5 853,99 36,03 ** 0,03 3 3 346,98 263,11 0,05 **Thoralus cranchii 3 4 557,14 664,91 ** ** 3 4 147,21 228,30 ** **Hippolyte varians 5 3 591,01 471,58 ** ** 2 2 206,39 199,48 0,23 0,02Pilumnus hirtellus 4 6 558,43 222,04 ** ** 2 4 221,59 139,13 0,08 0,02Pilumnus spinifer 4 4 448,60 292,23 ** ** 4 2 119,22 77,20 ** **Processa edulis 4 1 438,12 134,11 0,02 0,36 1 1 94,67 -47,64 0,07 0,31Xantho pilipes 6 5 416,78 292,35 ** ** 1 -47,64 0,31Xantho incisus 5 3 350,50 296,99 ** ** 1 1 -47,64 70,22 0,31 0,08Hippolyte sp. 1 1 318,66 182,25 0,12 0,29 1 2 93,91 -11,34 0,82 **Pirimela denticulata 6 2 424,29 103,93 ** 0,02 2 78,77 0,04Porcellana platycheles 3 3 442,98 150,48 ** ** 1 -16,51 0,14Palaemon longirostris 5 594,87 ** 2 -16,74 0,11Galathea strigosa 6 348,89 ** 2 164,14 **Eualus occultus 5 2 264,77 266,42 ** 0,05Percentage 87,5 64,3 75,0 57,1 75,0 57,1 56,2 50,0 ** p < 0,01 42,9 36,4 42,9 54,5 42,9 45,5 ** p < 0,01 Variable included  Variable included  Variable not included  Species not present in model (juveniles)  in model (adults)  in modelSampling siteHabitatSampling site Depth Exposure pROCKY BOTTOMS KELP HOLDFASTSDepth Exposure Degrees of Freedom AICDegrees of Freedom AIC pANALYSIS. Generalized linear models (GLM) were employed to determine the weighted effect of the environmental conditions over the spatial patterns of the postlarval community.  The best subsets procedure using the Akaike Information Criterion (AIC) was used to select the best model, and a normal log model was assumed. Null models were employed to extract common diversity patterns among variable combinations. Individual-based rarefaction curves (Gotelli and Graves, 1996), which generate comparative estimates of species number independently of the differences between sample size of the groups compared, were employed as a richness index. The probability of an interspecific encounter PIE (Hurlbert, 1971) was used as  an evenness  measure.  The abundance  levels  for  simulation  were  fixedSAMPLING. A stratified random survey was carried out along the coast of the Riade A Coruña (Galicia, NW Spain) during the months of July and August 1998, using a suction sampler operated by divers. Three sampling sites along the main axis of the Ria were selected to identify the meso-scale variability and an array of sampling locations   were   defined   within  each  site1 KMCANABALCANIDEPORTOCOBOaccording to the combination of three micro-scale variables: wave exposure, depth and habitat type. Four replicates were taken in each location. according to the sample with lowest abundance to allow the comparison among samples. Both evenness and rarefaction were estimated using EcoSim software (Gotelli and Entsminger, 2001), which uses a Monte Carlo procedure, and 1000 replicate simulations were performed for each estimate.Rocky BottomsPisidialongicornisAthanasnitescensThoraluscranchiiHippolytevariansPilumnusspp.ProcessaedulisXantho spp.PirimeladenticulataPorcellanaplatychelesPalaemonspp.GalatheastrigosaEualusoccultusKelp Holdfasts100500501005005010060402002040200204020020406050510201001020305051050510150510150246842024420241050510156420264202420240,20,00,20,40,60,40,20,00,20,00,20,40,60,000,040,080,120,00,10,20123PortocoboCanideCanabalExposedShelteredDepth 0Depth 1Depth 2HoldfastsNo. Ind/ holdfast JuvenilesAdultsPortocoboCanideCanabalExposedShelteredDepth 0Depth 1Depth 2CobblesJuvenilesAdultsRocksurfacesNo. Ind/ m2LITERATURE CITED.Gotelli, N.J. & Graves, G.R. (1996) Null models in ecology. Smithsonian Institution Press. Washington.Hurlbert, S.M. (1971) The non-concept of species diversity. A critique and alternative parameters. Ecology 52: 577-586Gotelli, N.J. & Entsminger, G.L. (2001). EcoSim: Null models software for ecology. Version 7.0. Acquired Intelligence Inc. & Kesey-Bear. http://homepages.together.net/~gentsmin/ecosim.htmThe GLM results for kelp holdfast samples showed a lower effect of all the factors on juvenile and adult patterns, with no observable differences among variables. A high proportion of the models obtained for this group of samples were not significant. This suggests that the influence of environmental conditions could be attenuated inside kelp holdfasts. These results, altogether with the ontogenic distribution patterns of the species found in holdfasts as well as the significant differences observed in diversity between them and rocky habitats, suggest that holdfasts are used as a temporary shelter rather than a nursery habitat.hypothesis that these areas constitute essential nursery habitats for benthic species.A lower specific diversity was found for adults than for juveniles in nearly all cases (Fig. 1). This difference was more pronounced in Canabal (the most external sampling site). Evenness values for both stages were high (Average PIE > 0.65) in most sampling locations (Table 1). The most internal site (Portocobo) presented a higher homogeneity in richness and evenness values for adults than for juveniles.The most abundant species occurred in higher density for juvenile over adult stages in most cases (Fig. 2).  All adults belonged to species also found for juveniles. Three main patterns of juvenile and adult distribution were identified: species without adult presence in the sampled area, such as Galathea strigosa; species that remain in the same area, but with observable ontogenic habitat shifts, which is the case of Eualus occultus and species that keep similar habitat use patterns along the life cycle, e.g. Pisidia longicornis.Although all the tested variables showed an important effect on the distribution of decapod species, variability in spatial patterns is mainly due to habitat type, which is a micro-scale operating factor.  Meso-scale variability related to sites along the Ria, as well as other micro-scale factors, i.e. depth and wave exposure, have a lower effect on spatial distribution of post-recruits.Sandy bottom coverage was significant only in sheltered areas of one sampling site and therefore GLM was not fitted. The diversity and evenness found in this habitat were very low due to the dominance ofthe Paguridea. Early juveniles of this group showed an average density of 427 Ind/m2 (Fig. 3), reaching 1227 Ind/m2 at 10 m deep. Data found support the hypothesis that these bottoms are essential recruitment habitats for this group.A similar pattern in the composition of parameters included in the most parsimonious models (GLM) was found between juveniles and adults on rocky bottoms (Table 2).  In both cases habitat type was the most frequent variable in models for the most abundant species (87.5% for juveniles; 64.3% for adults), while wave exposure shows the lowest percentage of occurrence in models for both juveniles (56.2%) and adults (50%).Paper available at www.udc.es/dep/bave/jfreire/home.htmRESULTS. Shallow bottoms of the Ria de A Coruña show a wide diversity of habitats and support a highly abundant and diverse  community   of   decapods.   Our  results  support  theFig. 1. Rarefactiondiversity curves. TheY axis represents theexpected richness fora given sample size(no. of individuals)Fig. 2. Densities of juveniles and adults of the most abundantspecies in different sites, exposure levels, depths and habitatsTable 2. GLM models for rocky bottoms and kelp holdfastsFig. 3. Densities ofjuveniles and adults ofthe group Paguridea in different sites, exposurelevels, depths andhabitatsPortocoboCanideCanabalSandy Holdfasts Cobbles Rock surfaces 10 m0 m 5 mHABITATJuveniles                                              AdultsDEPTHJuveniles                                              Adults051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150051015202510 30 50 70 90 110 130 150 170051015202510 30 50 70 90 110 130051015202510 30 50 70 90 110051015202510 30 50 70 90 110 130 150 170051015202510 30 50 70 90 110 130051015202510 30 50 70 90 110051015202510 30 50 70 90 110 130 150Average PIEVariancePIEAverage PIEVariancePIEDepth 0 0,525 0,00137 0,762 0,00026Depth 1 0,839 0,00018 0,689 0,00044Depth 2 0,206 0,00155 0,693 0Depth 0 0,861 0,0002 0,859 0Depth 1 0,795 0,0007 0,690 0,00086Depth 2 0,760 0,00069 0,664 0,00036Depth 0 0,870 0,00016 0,853 0Depth 1 0,886 0,00017 0,816 0,00023Depth 2 0,870 0,00021 0,805 0,00021Juveniles Adultos118169137Abund.levelAverage PIEVariancePIEAverage PIEVariancePIESandy 0,021 0,00026Holdfasts 0,566 0,00046 0,715 0Cobbles 0,451 0,00184 0,836 0,00005Rock surfaces 0,858 0,00014 0,716 0,0007Holdfasts 0,790 0,00023 0,774 0Cobbles 0,739 0,00094 0,667 0,00106Rock surfaces 0,856 0,00024 0,741 0,00048Holdfasts 0,860 0,00008 0,844 0Cobbles 0,861 0,00026 0,851 0,00006Rock surfaces 0,902 0,00009 0,815 0,0001Abund. levelJuveniles AdultosPortocoboCanideCanabal14313814850050100150200250300350400450PortocoboCanideCanabalExposedShelteredDepth 0Depth 1Depth 2CobblesJuvenilesAdultsRocksurfacesNo. Ind/ m2SandyTable 1. Evenness values2: 8-12 m1: 3-5 m0: IntertidalDEPTHKelp (Saccorhiza polyschides) holdfastsCobble and boulder poolsFlat rock surfacescovered with algaeRockybottomsSandy bottomsHABITAT TYPEShelteredExposedWAVEEXPOSURESPAIN43ºN42º8º W 7º50 kmPORTUGALRía de A Coruña

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Habitat diversity and postlarval benthic decapod crustacean assemblages in shallow waters of the Ría de A Coruña (NW Spain)

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