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1995 Fisheries and Oceanography off alicG ia, NW Spain: Mesoscale Spatial and Temporal Changes in Physical Processes and Resultant Patterns of Biological Productivity K. R. Tenore

M. Alonsonval

L. P. Atkinson Old Dominion University, [email protected]

J. M. Cabanas

R. M. Cal

See next page for additional authors

Follow this and additional works at: https://digitalcommons.odu.edu/ccpo_pubs Part of the Aquaculture and Fisheries Commons, Atmospheric Sciences Commons, and the Oceanography Commons

Repository Citation Tenore, K. R.; Alonsonval, M.; Atkinson, L. P.; Cabanas, J. M.; Cal, R. M.; Campos, H. J.; Castillejo, F.; Chesney, E. J,; Gonzalez, N.; Hanson, R. B.; McClain, C. R.; Miranda, A.; Roman, M. R.; Sanchez, J.; Santiago, G.; Valdes, L.; Varela, M.; and Yoder, J., "Fisheries and Oceanography off alG icia, NW Spain: Mesoscale Spatial and Temporal Changes in Physical Processes and Resultant Patterns of Biological Productivity" (1995). CCPO Publications. 136. https://digitalcommons.odu.edu/ccpo_pubs/136 Original Publication Citation Tenore, K.R., Alonsonoval, M., Alvarezossorio, M., Atkinson, L.P., Cabanas, J.M., Cal, R.M., . . . Yoder, J. (1995). Fisheries and oceanography off alG icia, NW Spain: Mesoscale spatial and temporal changes in physical processes and resultant patterns of biological productivity. Journal of Geophysical Research: Oceans, 100(C6), 10943-10966. doi: 10.1029/95jc00529 Authors K. R. Tenore; M. Alonsonval; L. P. Atkinson; J. M. Cabanas; R. M. Cal; H. J. Campos; F. Castillejo; E. J, Chesney; N. Gonzalez; R. B. Hanson; C. R. McClain; A. Miranda; M. R. Roman; J. Sanchez; G. Santiago; L. Valdes; M. Varela; and J. Yoder

This article is available at ODU Digital Commons: https://digitalcommons.odu.edu/ccpo_pubs/136 JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 100, NO. C6, PAGES 10,943-10,966, JUNE 15, 1995

Fisheries and oceanographyoff Galicia, NW Spain: Mesoscale spatial and temporal changesin physical processesand resultant patterns of biologicalproductivity K. R. Tenore,• M. Alonso-Noval,2 M. Alvarez-Ossorio,2 L. P. Atkinson,3 J. M. Cabanas4 R. M Cal,4 H J Campos,2 F Castillejo5 E. J. Chesney6 N. Gonzalez,2 R. B. Hanson,7 C. R. McClain,• A. Miranda,4 M. R. Roman, J. Sanchez,4 G. Santiago,1ø L. Valdes,2 M. Varela,2 andJ. YoderTM

Abstract. The Galician shelf off NW Spain (43N ø 9W ø) exhibitsmesoscale spatial and temporalchanges in biologicalproductivity associated with upwelling. Spatialheteroge- neity resultsfrom local geomorphicand land-seainteractions superimposed on the large scaleatmospheric processes that produceupwelling. Wind-inducedupwelling events, commonlyof short(i.e., week) duration, are more commonin the summerthan in the winter. A seriesof cruises,including some time seriessampling, and satelliteimagery analysisshowed that surfaceupwelling was more commonand persistenton the northern coastcompared with the westerncoast off the coastalembayments, the Rias Bajas. Nearshoreoff the rias, coastalrunoff, which is greaterin the rainy winter/springversus the dry summer,affected upwelling. In early summer,upwelling less often reachesthe surface because of increased water column stratification associated with lower surface salinitiesand thusupwelling is not detectedby satelliteimagery. Conversely,in late summer,upwelling more often reachesthe surfacebecause coastal runoff is reduced duringthe dry summermonths and the water columntends to be less stratified. Planktonbiomass and rate processesalong the Galician shelf reflectedboth ambient hydrographicconditions as well as prior historyof upwellingor downwelling. Phyto- planktonand bacterioplanktonwere in greatestabundance during upwelling conditions (Junethrough August); in contrast,both zooplanktonand fish larvae exhibitedhighest abundancesin March, when there were upwelling conditionsprior to our cruise. Spatial differencesin the durationand frequencyof upwelling events, in combinationwith advectionof water masses,are critical to the patternsof water columnproductivity and sardinefisheries production off the Galiciancoast. More persistentupwelling at this NW cornerof the Iberian peninsulasupports large sardinefisheries because zooplankton and larval fish populationshave time to respondto the higher primary production. Fartherdown the westernGalician coast,the episodicupwelling and resultantintermit- tent primary productiondoes not supporta stablefood supplyneeded to support fisheries.Times seriessampling revealed mean responsetimes of bacteria,phytoplank- ton, and zooplanktonto be on the order of a day, days, and weeks, respectively. Sardinesshowed no spawningresponse in the relativelyshort time seriessampling. The observeddistributional patterns of fish eggsand larvae showedsome offshore transport of fish larvaethat were spawnedinshore during upwelling periods and aggregationof larvae in a convergencezone northwestof Cabo Villano.

Introduction •ChesapeakeBiological Laboratory, CEES, Universityof Maryland, Solomons. The Galician (NW Spain) continental shelf with its 2InstitutoEspafiol de Oceanografia,LaCoruna, Spain. northern (Rias Altas) and western (Rias Bajas) coastal 3Departmentof Oceanography,Old DominionUniversity, embayments(Figure 1) supportssignificant pelagic and Norfolk, Virginia. demersalfisheries because of upwellingenrichment. In the 4InstitutoEspafiol de Oceanografia, Vigo, Spain. 5InstitutoEspafiol de Oceanografia,Fuengirola, Spain. rias, high primary productivityfrom the intrusionof up- 6LouisianaUniversities Marine Consortium,Chauvin. welled oceanicwater supportsan intensemussel raft culture 7SkidawayInstitute of Oceanography,Savannah, Georgia. [Tenore et al., 1982; Blanton et al., 1987]. The Ria de SLaboratoryfor Oceans,NASA GoddardSpace Flight Center, Greenbelt,Maryland. 9HornPoint EnvironmentalLaboratory, CEES, Universityof Copyright1995 by the AmericanGeophysical Union. Maryland, Cambridge. •øInstitutoEspafiol de Oceanography,Madrid, Spain. Paper number95JC00529. •GraduateSchool of Oceanography,University of RhodeIsland, 0148-0227/95/95JC-00529505.00 Kingston.

10,943 10,944 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

the westernU.S. coast, meteorologicalevems propagating from west to east are not affected by any meridionally continuousland massnorth of Cape Ortegal. The indemedcoastline formed by the Rias Bajasproduces significantorographic steering in the winds,resulting in a cv1 ß complex oceanic circulation over the narrow western cv3 © Galician continentalshelf [Blanton et al., 1984; McClain et al., 1986]. These effects includeboth local wind steering cv3• andcurrent-bathymetry interactions. The winds in therias ; cv4© are usuallyintensified, resulting in a wind stresscurl that can cause a flow reversal offshore of the shelf break. The bathymetrycauses additional complexity. During upwelling, I high-velocityand southward flowing jets are establishedand / ! may be deflected offshore by the topographicfeatures

ß extendingacross the shelf [Blantonet al., 1984;McClain et % al., 1986]. To even further complicatethe situation,local iV•t•M3 flow patternsrespond within a day to changesin wind de Arosa forcing. ',, ß ß Freshwaterrunoff varies geographically,being highest, A4•, Riade Pontevedra thoughseasonal, along the westernRias Bajasbut minimal along the northernRias Altas. When ranoff accumulates A1ß / alongthe westerncoast, as duringnortheastward winds, an I •, c•eVigo :: -. 0 25 50 alongshoregradient sets up that drives a northwardcoastal ;v,v •IGO • kmi • current. The runoff dischargecan influencethe strengthof lO 9 upwelling [Blanton et al., 1984; McClain et al., 1986]. Figure 1. The Galiciancoast of NW Spainshowing sam- During periods of high dischargefrom the Rias Bajas a plingstations along transects off the western(V indicating freshwaterlens extendsonto the shelf and caps upwelled off theRia de Vigo, A, off the Ria de Arosa;and M, off the water. Solar insulation contributes to stratification in the Ria de Muros) and northern (CV indicating off Cape springand may also maskupwelled water. Villano, C, off La Coruna; and O, off Cape Ortegal) coasts Thus upwellingalong the rias coast is complexboth occupiedduring the seriesof Fisheriesand Oceanography spatially and temporally becauseof irregular coastline, off Galicia (FOG) cruises. variable wind fields, and varying distributionsof runoff. Fisheriesand Oceanographyoff Galicia (FOG), a joim researchprogram of Spanishand U.S. scientists,focused on Arosaannually produces approximately 100,000 t of mussels oceanographicprocesses that would lead to mesoscalespatial [Perez and Roman, 1979]. Along the coast, purse seine andtemporal differences in biologicalproductivity and food fisheries for sardines,Sardina pilchardus, typically yields chainpatterns along the Galicianshelf. The presentpaper 100,000 t annually. Important demersalfisheries exist for emphasizesthe followingthree themesthat emergedfrom hake, Merluccius merluccius, and blue-whiting, Micro- this work: (1)Upwelling is more persistentoff Cape mesistiuspoutassou. Finisterreand along the northernversus the westernshelf. Coastalupwelling is fundamentallydriven by large-scale (2) Outwellingfrom the Rias Bajas, both of freshwaterand atmosphericprocesses, but localized geomorphologyand biogenicmaterials, influences coastal upwelling and related wind patterns can form complex temporal and spatial primaryproduction along the western shelf. (3) The biologi- patterns [Barber, 1988; Parrish et al. , 1983; Jury, 1988]. cal componentsof the shelfecosystem respond on different A seasonalnorth-south migration of the Azores High results timescalesto short-term episodic upwelling events and typically in alongshorewinds in summer (April through seasonalchanges in upwelling. September)that, combinedwith Ekman transport,uplifts subsurfaceNorth Atlamic Cemral Water (NACW) oreo the Materials and Methods shelf; during wimer, typical onshorewinds favor down- welling. However, in either season,shifting wind patterns We carried out four cruises aboard the R/V Cornide de causeupwelling and downwellingepisodes [Wooster et al., Saavedra as follows: June 16-26, 1984, September27 to 1976; Fraga, 1981; Blanton et al., 1984; McClain et al., October2, 1984, July 27 to August8, 1985, and 1986]. March 22 to April 2, 1986. We establishedthe following A diffuse frontal zone extendingnorthwest from Cape seriesof transects:on the northerncoast off Cape Ortegal Finisterredominates the generaloceanic circulation pattern (O), La Coruna (C), Cape Villano (CV), and on the western off Galicia [Fraga, 1981; Fraga et al. , 1982; McClain et coastoff the Rias Bajas off the Ria de Muros (M), the Ria al., 1986]. The from forms at the convergencebetween the de Arosa(A), andthe Ria de Vigo (V) (Figure 1). Individu- anticyclonicgyre in the Bay of Biscayand the weak north- al stationsalong these transects were numberedfrom 1 to 4 ward flowing currein west of Spain and Portugal[Swallow beginningoffshore. We measuredwater columnhydrog- et al., 1977]. Because of the abrupt change in coastal raphy, phytoplanktonbiomass and productivity,micro- and direction at Cape Finisterre, upwelling will occur some- macrozooplanktonbiomass and speciescomposition, and where along the Galician coast throughout270 ø of wind macrozooplanktongrazing rates, bacterial abundance,and direction [McClain et al., 1986). In comrastto conditionsoff production,and ichthyoplanktonspecies composition and TENORE ET AL.: OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,945 abundance. The samplingstrategy of the first two cruises Microbiology differed from cruises three and four. On the first two Ratesof tritiatedthymidine incorporation into trichloro- cruisesall the transectswere sampledonly onceto get a aciticacid (TCA) precipitablematerial were determined by spatialdistribution of hydrographicand biological properties. the methodof Fuhrmanand Azam [1982]. Two replicate On the third cruise, transectsA and CV were sampled andone TCA-killedcontrol (to measureabiotic adsorption multipletimes to study short-termtemporal responses in of label) 30-mL seawatersamples were inoculatedwith hydrographyand biological parameters to upwellingevents. 0.1 /xCimL -1 3H-methyl thymidine and incubated on board For the fourth cruise we added transect C to increase areal shipin the dark for 1 hour at surfacewater temperatures. coverage. Bacterialgrowth rates were estimatedfrom sampledilution experiments[Kirchman et al., 1982]. Bacterialabundance Hydrography,Meteorology, and SatelliteImagery was determinedby countingpreserved samples stained with acridineorange [Hobble et al., 1977]. Thesedata were used Temperatureand salinitymeasurements were made with to convertin situthymidine uptake data (picomoles per liter a Neil Brown Mark III conductivitiy-temperature-depth (CTD) profiler. Water samplesfrom Niskin bottleswere per dayto cellsper literper day[Kirchman et al., 1982]). analyzedfor nutrientsusing methods described by Glibert Zooplankton and Fish Larvae andLoder [1977] and Strickland and Parsons [1972]. Wind dataderived from pressure field maps were used to compute Macrozooplanktonand ichthyoplanktonwere sampled upwellingindices as describedby Blantonet al. [1984]. during the day with a paired opening-closingnet frame NOAA 7 advancedvery high resolution(AVHRR) (60 cm diameter) fitted with 202- and 333-/xm mesh nets. satellitedata were used to calculatesea surface temperatures Distance during each tow was estimated with General usingStrong and McClain's [1984] algorithm. Nimbus7 Oceanics flowmeters. Two depth intervals, the surface coastalzone color scanner(CZCS) satellitedata were used mixed layer (30-50 m) and below the mixed layer to 100 m, to calculatechlorophyll pigment data using the atmospheric were sampledat each station. The sampleswere preserved correctionand bio-optical algorithmsof Gordon et al. in 5 % formalinfor later analysis. [1983]. Zooplanktonbiomass caught in the 202-/xm mesh was determinedfrom displacementvolumes measuredat least 6 weeks after preservationto avoid bias due to variable Phytoplankton sampleshrinkage [Wiebe et al., 1975]. Biomasswas calcu- Water samples were collected with Niskin bottles at lated from displacementvolumes by log C (milligrams of isolumedepths of 100, 50, 25, 10, and 1% lightpenetration carbonper cubic meter) = log displacementvolume (cubic determinedwith an underwaterphotometer (Kahl Instru- centimeterper cubic meter) q- 2.2092/1.069 [Romanet al., ments,model 268 WA 310, first two cruises)or Secchidisc 19851. (last two cruises). Incidentirradiance was continuously Fish eggsand larvaewere sortedand identified to species monitoredduring cruises with a LI-COR LI-190S quantum when possible. Eggs of sardines,Sardina pilchardus, were sensorand LI-550 integrator. separatedinto three stagesof developmentand classifiedas Chlorophylla (chla) andphaeopigments were determined living or dead. Sardinapilchardus larvae were measuredto usingthe fluorometricmethod of Yentschand Menzel [ 1963] the nearest0.1-mm standardlength (SL) for length-frequen- as describedby Strickland and Parsons [1972]. Water cy analysis. sampleswere filteredthrough Gelman type A glassfiber Microzooplanktonwere collectedby a submersiblepump filters (total size fractions)or, alternatively,were first and hose(5-cm diameter)system. Seawaterflowed at 22 L filteredthrough 12-/xm Nucleopore polycarbonate filters and min-• throughshipboard sensors for measuringtemperature, then the filtrate was filteredthrough Whatman GF/C filters conductivity,and fluorescence and was concentrated through (< 12-/•m size fraction). Phytoplanktonspecies were a submerged20-/•m mesh net on deck to collect microzoo- enumeratedusing the Utermohl [1958] techniquewith plankton. Microzooplanktonwere collectedfrom below the 100-mLsettling chambers and 250 or 400x magnification. mixed layer and above as indicatedby the temperature Primaryproduction (carbon uptake) was determinedby profile of water collectedon the pump'sdescent. Microzoo- incubatingsurface seawater with 14Cbicarbonate in 125-mL planktonwere preservedin 4 % buffered formalin and later Pyrex bottlesplaced into bagsmade of varying layersof enumeratedto taxonomicgroups. screen to simulate in situ irradiance levels at different Zooplanktongrazing was estimatedby the uptakerate of depths.Two light andone dark bottle for eachwater depth •4C labeledparticulate matter [Daro, 1978; Roman and were incubatedfor 4 hourson shipdeck in runningsurface Rublee, 1981]. Water collectedfrom the mixed layer was seawater. Size fractionation was the same as described for dispensedinto 1-L polycarbonatebottles and inoculatedwith chl a andphaeopigments but using0.8/•m Millipore filters. •4C-bicarbonate(50/•C L'I). The bottleswere incubated for Nitrateuptake was determinedusing the stableisotope 1 hour at 60% light on boardin flowingsurface seawater. method(15NO3-) of Dugdaleand Goering [1967]. Polycar- Macrozooplanktoncollected by shorttows in themixed layer bonatebottles containing 500-mL sampleswere inoculated were added to the bottles after ! hour incubation with 14C. with 0.2 •tm of 15NO3-,incubated for 4 hours,and then the After 30, 60, and 90 min, replicatebottles were removed, contentsof the bottleswere filtered throughpreviously the zooplanktonwere concentratedon 200-/•m mesh,filtered combustedGelman glass fiber filters (type A). Isotope onto 12-/•m preweighedfilters, washedwith 10% HC1 and ratioswere determinedwith a Jascoemission spectrometer. water, dry weight(DW) determined,and isotopecontent of Equationsgiven by Yoderet al. [1983] were usedto calcu- the zooplanktonmeasured. The < 200-•tmparticulate frac- late NO3-N uptake. tion was filtered, and the isotopeactivity was measured. 10,946 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

6000 1984Upwelling Index-West Coast ] 2500[ 1984Upwelling I -600 4000r •. _. /il . I I ooo -oo ,, t AI• -800 - • • " o,,soo•/• / ,ooo -1000 I L/ Jan, Feb , Mar Apr May June July Aug Sept' Oct , Nov , Dec Oh16 18, 20, ", 22 24, 26, •7 •8 •9 •0 1 2-1200 J•e Sept Oct 6000 200 1984 UpwellingIndex- North Coast 1984 Upwelling

4000 -•.

x 20O0 x _ -200 c

..• o Jh, I .. .__c -400 • • -2000 •,, I I tl -4000 -600I -6000t -800 -80001 Jan •Feb •Mar , Apr ,May ,June • July i Aug 'Sept'Oct ' Nov ' Dec 16 1• •0 2'2 2•4 2• •7 •8' 2•9 3•0 • •-1000 June Sept Oct Figure2. Calculatedupwelling indices for the (top) west and (bottom) north coasts of NW Spainduring 1984 and, specifically,during the summer1984 and fall 1984cruises.

Zooplanktongrazing rateswere calculatedby disintegrations andsubsurface temperatures were highestoff the Rias Bajas; per minute (dpm) zooplanktonmilligram of DW per liter temperaturesat 50 m depth were the same or lower than at equalsliters filtered milligram zooplanktonDW per weight 50 m off the Rias Altas. Low oxygen values observedoff per hour. Weight-specificfiltration rates were multipliedby the Ria de Arosa suggestconsiderable outwelling from that the zooplanktonbiomass to estimate in situ grazing rate ria, which couldhelp to explainwhy the upwellingwas not equalsliters filtered per cubicmeter per hour. manifestat the surface. On June 18 the surfacepigment concentrationsexceeded 3 mg m-3 off Cape Finisterreand Results were greaterthan 1.5 mg rn-3 off the Rias de Arosaand de Vigo. The high concentrationsoff Finisterrecorresponded Summer 1984 (Cruise dates, June 16-26): Prevailing with the area of low surface temperatures. Isopycnals Upwelling Conditions indicatedupwelling on three occupationsalong transects off Physicaloceanography. Winds were generally upwelling the Arosa (June 18, 20, and 28). favorablealong both the northernand western coasts during Phytoplankton. Vertical distributionsalong the western the cruiseand were mainly from the NE up to 13 ms-i shelf at nearshore stations V4 and M4 show the effects of (Figure2). Windshad been upwelling favorable along both outwelledwaters on nutrients,chl a, and primaryproduction coastssince June7, increasingsteadily in strengthuntil (Figures4a-4d). Nitrate concentrationswere relativelylow subsidingon June 22-23. Satellitesurface temperatures in the near-surfacelayer comparedto the coastalstations showedupwelling localized off Cape Ortegaland Cape farther north (CV4, Figure 4d). Furthermore, vertical Finisterre,with upwelling at thesurface visible west of Cape distributionof primary productionwas bimodal at stations Finisterre(Plates la and lb). Water columntemperature V4 and M4, suggestinga high light-adaptedphytoplankton datacollected during the cruiserendered a slightlydifferent populationin the layer of outwelled water. At all coastal interpretation. Uplifted isothermsoccurred off Rias de stations,concentrations of NO-3-Ngenerally exceeded 5 rim Arosa (Figure3) and de Vigo, indicatingsubsurface up- near the baseof the euphoticzone (30-40 m deep). wellingalong the morewestern portion of the shelf. Nitrate Depth-integratedprimary production and chl a were valuesat 50 m depth on June 18 in the Rias Bajas and generallyhigher near the coast(V4, A4, M4, and CV4) than adjacentshelf exceeded 8 rim, but were 5 to 8 rim at other near the shelf break (A2, M2, and CV2) (Table 1 and areas on the shelf. By June 28 nitrate concentrationsat Figure5). Mean chl a andprimary production were 90 mg 50 m were greaterthan 15 tzmnear the Rias de Arosa and m-2 and 1.23 gC m'2 d'l, respectively,at the four coastal de Vigo and were generallybetween 10 and 15 rim else- stationscompared with 33 mg m-2 and 0.78 gC m-2 d 'l at the where, indicatingthat upwellinghad intensified. Surface three offshore stations. TENORE ET AL.. OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,947

CAPE ORTEGAL

CAPE FINISTERRE

.•:-•. '•" R I A d ß MUROS

•'•'"m. •m• • RIA •l AROSA

R IA •le PONTEVEBRA

RIA •le VIGO

N.W. SPA IN SEA SURFACE TEMPERATURE NASA GSFC 6 1884

Plate la. Satellitephotograph of sea surfacetemperatures along the coastof NW Spainon June 18, 1984. The following are the color definitionsfor surfacewater temperatures- dark blue, 12 to 13"C' purple, 14øC;light blue, 15øC;yellow, 16øC;amber, 17øCß orange, 18"C; and red, 22øC. Black indicatesland while white is cloud cover.

Phytoplanktonpassing through a 12-/xm filter were a numbers increased from about 3 x l0 s mL -I on transect V to relatively small proportionof chl a (28%) and primary over 7 x l0 s mL -• on transect M. Numbers nearshore were production(32%) at the four coastalstations but accounted about twice those at the shelf break. At the shelf break, for two thirds of both chl a and primary productionat the numbers found near the bottom of the water column were three offshore stations(Table 1). Net phytoplanktonwere similar to those measured at the surface. On the northern dominatedby the following diatoms: Chaetocerascom- shelf, at transectCV, numbers decreasedfrom 4 x 105 mL -• pressus,C. decipiens,C. lauderi, Rhizosoleniaalata, R. at the nearshorestation to 3 x 105mL -• in deepwaters near imbricata,R. shrubsolei,Schroederella delicatula, Stephano- the shelf break. Highest numbers of bacterioplankton pyxisturris, Nitzchiaseriata, and Lauderiaborealis. Most occurredon the northernshelf on transectsC and O. Along nanophytoplanktonwere eithersmall flagellates with a mean transectC, bacterioplanktonnumbers reached concentrations diameter of 3 to 6 ttm or small naked dinoflagellates of 1.4 x 105 mL -•. (Gymnodiniumand Amphidiniumtypes) with a diameterof We comparedbacterioplankton biomass estimated from 8to 10/xm. bacterialcell numbers(using a conversionof 20 /xgC per Microbiology. Bacterioplanktoncell numbersvaried cell) from Figure 6 to phytoplanktonchl a biomass(using vertically and horizontally on the northern and western 50/xgC per microgram chl a) from Figure 5. Bacterio- shelves(Figure 6). On the westernshelf, bacterioplankton planktonnear the coastwere only 5 to 20%, but at the shelf 10,948 TENOREET AL.' OCEANOGRAPHYOFF GALICIA, NW SPAIN

CAPE ORTEGAL

CAPE FIHISTERRE

R I A •1 MUROS

RIA •te AROSA

RIA • PONTEVEDRA

RIA ae VIGO

N.W. SPAIN SEA SURFACE TEMPERATURE NASA GSFC 6 25 84

Plate lb. Same as Plate l a, but for June 25, 1984.

break were 40 to 70% of the phytoplanktonbiomass. Size- temperatureminimum, nauplii abundancesin the water fractionationdata of the phytoplanktoncommunity showed columnbetween 15 to 35 m were higher than between0 to thatin nearshorewaters, net plankton dominated and bacteri- 15 m. Bivalve larvae rangedfrom 0.3 to a maximumof 13 al biomass was a small percentageof the phytoplankton ind L -• and crustacean larvae showed a maximum of 12 ind biomass,whereas in offshorewaters, nanoplankton dominat- L '• at station A3. ed and bacterialbiomass equaled phytoplankton biomass. Weight-specificzooplankton grazing rates rangedfrom Zooplankton. Zooplanktonbiomass ranged from 0.9 at 118 to 531 mL mgC-• h'• (Figure 8b). When theseweight- stationC3 (50 to 100 m) to 72.5 mgC m-3 at stationC2 specificrates are multipliedby the zooplanktonbiomass, we (0 to 50 m) (Figure 7). The ratio of zooplanktonbiomass in can estimatethe grazingimpact of the zooplanktoncommu- the surface 50 m versus 50 to 100 m ranged from 1.2 to nity. The two highestgrazing rates were foundon transects 16.2 andaveraged 5 mgC m-3. Thusmost of the zooplank- A and C, where zooplanktonremoved an estimated77 % of ton were concentratedin the surfacemixed layer. phytoplanktonstanding stock per day. Copepodnauplii rangedfrom 2 to 12 individuals(ind) Ichthyoplankton. The five most abundantfish larvae L -• (Figure 8a). On the northernshelf, where upwelling composed75% of the total catch. They included the reachedthe surface,nauplii abundancesin the water column sardine, Sardina pilchardus (49%), the dragonet, Cal- between 0 to 15 m were higher than between 15 to 35 m. lionymuslyra (14%), labridae (12%), the scad, Trachurus In contrast, on the western shelf on transect A, where there (8 %), and the scaldfish,Arnoglossus laterna (6 %). Mean was an upwelling-relatedsubsurface nitrate maximumand abundances of fish larvae were 29 ind 100 m -3. Densities TENORE ET AL.. OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,949

Surface (Om)Water Temperature 50m Water Temperature June 1984 Cruise June 1984 Cruise

ß " 14.0 _.• /' 12.4 13.6--' • ...' La Coruna 13'2'•"•I•'••'-"• LaCoruna 12.8/"12;4 • : / CaboVillano

Finnistera 'ii i, CaboFinnistera Rla de Muros ?, [ Riade Muros

12.8 Rla de Arosa "" Rlade Arosa 13.2'-• \\

Rla de Pontevedra Rla de Pontevedra ,./J• RladeVigo ,..,.•I Ria de Vigo •' Vigo -' / I v'.•o

Figure 3. (left) Surfaceand (mi.ddle) 50-m watertemperatures (degrees Celsius) along the coastof NW Spainand (right) vertical temperature profiles off the Ria de Arosaduring the June1984 cruise. were greatestnearshore on transectsV, CV, and C and thermson the Vigo (V) transectdo not correlatewell. The lowest off transectM (Figure 9). CZCS data on September24 (not shown)indicate highest Sardine larvae were more abundant and significantly seasurface pigment concentrations were nearshoresouth of larger offshore(V2, A2, C2, and CV2) from transectCV Ria de Vigo, with a diffuse enhancementin a broad area west down to transectV (Mann-WhitneyU-test, probability from La Coruna to the Portugueseborder. Minimum (p)=0.05). North of Cabo Villano, sardinelarvae were surfacetemperatures of lessthan 14øCwere observedat the more abundantoffshore but were not significantlydifferent nearshorestations along transectV and, accordingto the in lengththan thosecollected at nearshorestations [Chesney satellite data, were colder farther west. Moderately cool and Alonso-Noval,1989]. Sardineegg abundances(data not water extended around Cabo Finisterre to La Coruna and shown), in contrastto larvae, were distributedclose to shore coincided with the region of slightly enhancedpigment and were abundant at stations C4, CV4, and A4. concentrations observed with CZCS. The coastal SSTs from Sardinelarval densitieswere significantlygreater (Mann-- the AVHRR and ship observationsdecreased in the region Whitney U-test,p=0.02) on the northerntransects (x=20.0 betweenCabo Ortegaland Ria de Vigo from September25 100 m-3) than on the westerntransects (x=7.8 100 m-3). to October2. This dropindicates that upwelling had intensi- Similarly, densitiesand distributionof other fish larvae fied and that the general area of colder temperaturesand showed distinct distribution differences between the northern enhanced pigment concentrationcircumscribing Cabo and western coasts. The scad Trachuruswas significantly Finisterre had increasedin size. A secondCZCS image on more abundant (Mann-Whitney U-test, p=0.05) in the September29 confirmsthis interpretation.However, the northern shelf, while the labrid Ctenolabrusrupestris was pigmentconcentrations were low comparedwith previous more abundanton the western shelf off the Rias Bajas, but observationsmade in this area [McClain et al., 1986]. At thosedifferences were not statisticallysignificant. 50 m, minimum temperatureswere found off the Ria de For every cruisewhere the datawere availablean attempt Vigo. Surfacenitrate concentrationswere highest(> 5 ttm) was made to look at the distribution and abundance of fish off the Rias Bajas. Thus the AVHRR SST and CZCS larvae in relation to microzooplanktonand abundanceof pigmentimages show similar patternsand trends:surface sardineeggs in relationto concentrationschl a. There were temperaturesdropping and pigment concentrations increasing no significantcorrelations with either of thesevariables. with time. Phytoplankton.As in June1984, NO-aconcentrations at Fall 1984 (Cruise dates, September 27 to October 2): all coastalstations generally exceeded 5/tm near the baseof PrevailingUpwelling Conditions the euphoticzone (1% surfacelight) at 30 to 40 m deep Physicaloceanography. Winds prior to and during the (Figures4a-4d). There were no consistentdifferences cruise were from the southwestand downwelling favorable within coastal or offshore stations. A mean chl a concentra- along both north and west coasts(Figure 2), but the down- tion of 47 mg chl a m-: andprimary production of 0.46 gC welling was relatively weak. Satellitesea surfacetempera- m-: d4 at the four coastalstations compared with 36 mg ture (SST) (Plates 2a and 2b) and subsurfacehydrography chl a m-: and 0.78 gC m-: d4 for the two offshorestations (Figure 10) both indicatedweak upwelling to the southoff (Figure 5 and Table 1). the Rias Bajas and downwellingnorth of Cape Finisterre. Phytoplanktonpassing through a 12-/tm filter accounted Apparently,the wind had a sufficientsouthward component for a relativelyhigh proportion,averaging 60%, of chl a to force some upwelling south of Cabo Finisterre. The and primary productionat the coastalstations (Table 1). upwelling indices and the upward trend in nearshoreiso- The < 12-/tmfraction accounted for virtuallyall of the chl a 10,950 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

A STATION V4 STATIONM2 June Sej3tember NO3 NO3 S

NHNO43 ß NO3 40 a [I !"1po 4 O NH4 Chl a 40 1:3PO 4 0 2.5 5.0 0 2.5 5.0 Chl& 0 I 2 0 I 2 0 I , I I E ! t _ø--E 20 t $nano O net • 20

4O Primary Production I, !•o 0 2.5 5.0 0 2.5 5.0 ¾'ø7' 0 - I...u I I I 40J;••Pr t' 0 I 2 0 I 2 0 i

20

.J O net r 40 20 i i/ nano

40

C STATIONM4 STATIONCV4 June September June September NO3 NO3 0 10 2O 0 10 20 I ,I I I I I 5• lOI oI 5I lOf •H 4 NH4 2.5 5.0 0 2.5 5.0 0I 2.5I 5;0 0I 2.5I, 5.0I I I I I I PO,• PO4 o !.o 2.o o !.o 2.0 0 1 2 0 I 2

ß NO3 40-J j aPO,• Chl a Chl a 0 2.5 5.0 0 2.5 5.0 0 I 2 0 I 2 ß 0 •; •1

ß' 20 / [• , C3 nano net 0 net 40 4o Primary Production Prtmnry Prod.clion 02..55.0 02.55.0 O ,5 IO 0 5 IO

2ø1; // 20o? ,• I• O not 40-•'J •" '1'J o 40 J [3I:

Figure4. Verticalprofiles of nutrients(NO3, NH4, and PO4, in micrometer),chlorophyll a (micrograms perliter), and primary production (micrograms of Carbonper cubic meter per hour) during the June 1984 andSeptember 1984 cruises at stations(a) V4, (b) M2, (c) M4, (d) CV4 alongthe coastof NW Spain. See Figure ! for stationlocations. TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,951

Table 1. Chlorophylla and Primary Production,and the < 12-ttm Size Fraction Percentage Contributionat Coastaland Offshore Stationsfor the June 1984 and September1984 Cruises

Chlorophylla PrimaryProduction ß mg m-2 Percent< 12 ttm gC m-2 d '• Percent< 12 ttm

Station June Sept. June Sept. June Sept. June Sept.

Coastal

V4 144 49 - 45 0.57 0.32 35 35 A4 60 70 29 62 0.64 0.74 68 67 M4 107 44 30 59 1.79 0.48 19 56 CV4 48 24 24 86 1.92 0.30 7 90 Mean 90 47 28 63 1.23 0.46 32 62 Standard 44 19 3 17 0.72 0.20 26 23 deviation

Offshore

A2 17 30 67 98 0.47 0.39 86 98 M2 30 41 88 99 0.32 1.16 80 91 CV2 53 - 13 - 1.54 - 12 - Mean 33 36 56 99 0.78 0.78 59 95 Standard 18 - 39 - 0.67 - 4 - deviation

and primary productionat the offshore stations(Table 1). (Figure 11). Two estimatesof bacterialgrowth in the water Microflagellatesranging from 2 to 5 /zm in diameter column,one based on initial ratesof thyroidincincorporation dominatedthe nanoplankton. Net phytoplanktonwere and cell number and one based on in situ cell dilution dominatedby the followingdiatoms' Rhizosolenia delicatula, experimentsand changein cell abundanceover time, were R. stolterfothii,R. shrubsolei,and Thalassiosirasubtilis. generallywithin a factorof 1 or 2 of eachother. However, Microbiology. During this cruise, estimatesof in situ along transect V, in situ bacterioplanktonpopulations growthrates of bacterioplanktonvaried between the northern appearedto be active from initial growth rate estimates (CV andO transects)and western (V andA transects)coasts (thymidine incorporation), but they did not appear to

July-August1985 B 150 June1984 A 100

100

50

50

0 o 432 432 432 4'32 432 42 42 v A M CV C A CV

150 c D September 1984 March-April1986

100

50 Or 432 432 432 432 432 432 42 42 42 V A M CV C O A CV C

Figure 5. Phytoplanktonbiomass as chlorophylla at stationsalong the coastof NW Spainduring the four FOG cruisesin (a) June1984, (b) July/August1985, (c) September1984, and (d) March/April 1986. Data are given as meanwith barsrepresenting 1 standarddeviation. See Figure 1 for transectand stationloca- tions. 10,952 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

14 Highest concentrationsor' zooplankton were found on June 1984 transect CV and on the western shelf transects M and A. 12 Similarto June,there were more zooplanktonin the surface (0 to 50 m) comparedwith the subsurface(50 to 100 m) 10 water column, an averageratio of 2.6 (range 1.7 to 5.0). Copepodnauplii ranged from < 1 to 8 ind L 'l with highestabundances at stationsM4 and 04 (Figure 8a). The highestabundances (3 ind L -1)of bivalvelarvae were found off the Ria de Arosa at station A4. Weight-specificzooplankton grazing ranged from 21 to 355 mL mgC-1 h'l (Figure8b). Water columnclearance rates (weight-specificrates multiplied by biomass) were lower thanJune values. The averagefor all stations,3.1 L m-3 h -1, extrapolates to approximately6% of thephytoplank- ton standingcrop grazed per day. 432 432 432 234 234 Ichthyoplankton. Mean densityof fish larvae was 3.5 V A M CV C 100m -3, reflecting the low periodof annualspawning in the area. No derailedanalysis of the fish larvae data was made, Figure 6. Bacteriacounts for surfaceand bottomwater at and graphics of the abundancedata were not included stationsalong the coastof NW Spainduring the June 1984 becausespecies diversity and abundanceof fish larvae were cruise. See Figure 1 for transectand stationlocations. low, indicatinglow spawningactivity. A totalof only a few hundredlarvae were taken in all the samples. The larvae collectedwere almost exclusivelyone species,the goby, increasesignificantly over time in the dilutionexperiments. Crystallogobiuslinearis. On the basis of these experiments and measurements, bacterioplankton on the northern shelf were active and Summer 1985 (Cruise dates, July 27 to August 8): dividing, whereasthose on the westernshelf were growing Prevailing Upwelling Conditions slowly. Interestingly,highest bacterioplankton growth rates were foundin a regionwhere 70 to 90% of the phytoplank- Physicaloceanography. The calculatedupwelling index ton were nanoplankton. indicatedthat weak upwelling conditionspersisted during Zooplankton. Zooplanktonbiomass ranged from 6 at most of July (Figure 12). During the cruise, winds were station02 to 107 mgC m-3 at stationM2 (Figure7b). initiallystrongly downwelling favorable (SW) alongthe west

120June 1984 _September1984 A B

60

0 432 432 432 432 432 432 432 432 432 432 v A M CV C V A M CV C O

July/August1985 March/April1986

120 - c D

60

432 432 4321 4321 4321 A CV A M C Figure 7. Zooplanktonbiomass concentrations (milligrams Carbon per cubicmeter) in the surface50 m at stationsalong the coastof NW Spainduring the four FOG cruisesin (a) June1984, (b) September1984, (c) July/August1985, and (d) March/April 1986. Data are givenas singlevalues or means,with bars representingthe standarddeviation of the mean. See Figure 1 for transectand stationlocations. TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,953

Ai June 1984 September 1984 15- 8-

10

V4 A3 M3 CV3 03 V4 A4 M4 CV3 04 15 July 1985 March 1986 40 1 E]o-15 rn

20

0 io- A4 A2. OV40V2 r,,A4 A2 CV4 CV2 C4 C2

el 600 June 1984 September 1984

3O 40O

cn 200 E lO E ß E u) 0 0 • v3 A4 M4 CV2 C2 A4 A3 04 03 04 03 • 600 July 1985 March 1986

.__.

(..o 400

200 -10

o A4 A2 CV4 CV2 A4 A2 CV4 CV2 C4 02 Io

Figure 8. (a) Copepodnauplii densities (per liter) in the surface15 m (dotted)and 15 to 30 m (stippled) waterdepths and (b) weight-specificzooplankton grazing rates (milliliters per milligramCarbon per hour) (dotted)and communitywater columnclearance rates (liters filteredper cubit meter per hour) (stippled) in the surface50 m at transectstations along the coastof NW Spain duringthe four FOG cruisesin June 1984, September1984, July/August1985, andMarch/April 1986. Data are plottedas eithersingle values or means,with barsrepresenting the standarddeviation of the mean. SeeFigure 1 for transectand station locations. coast, shiftingmidway, and remainingweakly upwelling July 30 and August 3 did indicate brief upwelling in re- favorable for the remainder of the cruise. However, winds sponseto the wind event on July 31. Note the abrupt were upwellingfavorable off the northerncoast, with a decreasein nitratedistribution on transectV betweenJuly 30 strongsustained event beginningon July 29. The CZCS and August 3 and the increaseon transectA from July 29 to imagery(not shown)indicated a broad area of enhanced August6. A strongthermocline was present at moststations surfacepigment extendingoffshore of Cabo Finisterre, because of surface heating, with highest surface water reflectingthe weakupwelling situation along the northcoast temperaturesobserved offshore. duringJuly. The hydrographyon transectsV andA showed Phytoplankton. At nearshorestations off Villano (CV4) weak upwelling(Figure 13). Subsurfaceisotherms (e.g., and Arosa (A4) temporal changesin mean euphotic zone 12øC)rose with time west of Finisterrebut remainedfairly chl a and primary productionshowed opposite trends (Fig- constantto the north, althoughthe Villano section(CV) on ure 14b). On the northern shelf stationCV4, both chl a and 10,954 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

E] Otherlarvae 500 • Sardine Scale- per100 rn •

Ortegal

LA CORUNA

!Cabo;•illano

ß ß ß ,

ß ß Finisterre

ß . I , ß ß ,

ß ß .

..

\ r= Ria•e Uuros

?.:.'."'.ß . 'RIASBAJAS' :. Riade Arosa

• • f Ri•.dePontevedra ..

.

• • " Ri••;Vigo 0 25 5O

, ! VIGO km 10 ø 9• Figure 9. Densitiesof fish larvae at stationsalong the coastof NW Spainduring the June 1984 cruise. primaryproduction decreased with time. On July28, chl a westernshelf, primary productionand chl a increasedfrom was 6 mg m-3 but was < 1 mg m-3 on August7, 10 days July 29 to August8. On July 29, primary productionand later. A CZCS image from July 30 showedthat the highest chl a were <2 mg m-3 h -1 and 2 mg m-3, respectivelyß On pigment concentrationswere centeredbetween La Coruna August8, primaryproduction was 7 mgC m-3 h -1, and chl a (C) and Ria de Muros (M), with the highestvalues (> 2 mg was almost5 mg m-3. Increasingrates of primaryproduc- m-3) off Cape Villano (CV). Primaryproduction was not tion and concentrationsof chl a from July 28 to August 8 measuredon July 28 on transectCV. However, primary coincidedwith decreasingsurface temperatures and increas- productiongenerally decreasedfrom July 30 to August 7. ing nitrate levels associatedwith coastalupwellingß In sharp contrastto the northern shelf, on transectA on the At the offshore stations on both transects CV and A there

o

40 40

80 80 - "'" '--' - 14•' •,- -.- .... '--' 13 .-,,,• 120 20 -'- ø 1• ..,,, 160 60 --

2OO :oo -- \ VIGO TRANSECT ORTEGAL TRANSEC 24O Temperature •4o _ Temperature September1984 28O September1984 I I I I I I /I I 40 20 10 0 •0 15 10 5 0 Distance(kin) Distance(krn) Figure10. Verticaltemperature (degrees Celsius) profiles with distancefrom coast on the transectsoff (left)Vigo and (right) Ortegal (see Figure 1 for locationsof thesetransects) in September1984. TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,955

CAPE ORTEGAL

CAPE FINISTERRE

R A d MUROS

R ! A d AROS ß

RIA ß PONTEVEI)RA

RIA 4 VIGO

N.W. SPAIN SEA SURFACE TEMPERATURE NASA GSFC 9 5 8

Plate 2a. Satellitephotographs of sea surfacetemperatures along the coastof NW Spain on September 25, 1984. The following are color definitionsfor surface water temperatures:dark blue, 12 to 13øC; purple, 14"C; light blue, 15øC;yellow, 16øC;amber, 17øC;orange, 18"C; and red, 22"C. Black indicates land, while white is cloud cover.

were no clear trendsin primary productionand chl a during To compare bacterioplanktonto phytoplanktonproduc- the time series,except that chl a concentrationsoffshore on tion, rates of thymidine incorporationwere converted to transectCV decreasedfrom approximately3.0 to 0.5 mg bacterioplanktonproduction using 2 x 1048cells mole -• of m-3. Thesechanges cooccurred with an approximate3"C thymidineincorporation and 1 x 10-•4 gC cell4. Or/' the rise in surfacetemperature (14a). western shelf, bacterioplanktonproduction decreased as a Microbiology. In 1985, time seriesstudy showed short- percentageof phytoplanktonproduction from 10 to 3%, term changes(days) in thymidineincorporation and bacterio- whereason the northernshelf, bacterioplanktonproduction plankton numbers in surface waters on the northern and increasedfrom 5 to 30%. Bacterioplanktonwere 25 % of western shelves (Figure 15). Rates on the western shelf the phytoplanktonon the western shelf but nearly equaled were higher but more variable than rates on the northern phytoplanktonbiomass on the northernshelf by the end of shelf (Table 2). During the 10-day time series, rates in- the time series. Phytoplanktonbiomass decreased over time creasedon the northern transectCV, whereas rates cycled on the northern shelf. througha minimum value on the western transect. Zooplankton. The variabilityand amount of zooplankton Bacterioplanktonabundance covaried with thymidine were greatest at station A4, nearshoreoff the Ria de Arosa incorporation on the short-term (days) on both shelves (Figure 16a). At stationA4 (0-30 m), zooplanktonbiomass (Figure 15). Bacterioplanktonabundance in bottom waters decreasedfrom 120 to 48 mgC m-3 duringthe time series remainedconstant over the time series. Averagebacteriopl- samplingbut then increasedon the last samplingday. On ankton abundance on the western and northern shelves was transect CV the biomass decreasedonly slightly, with a not significantlydifferent (Table 2). slightincrease at stationCV4 on the last samplingday. The 10,956 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

C-PE ORTEGAL

CAPE FINISTERRE

R I A •1 MUROS

RIA 4 AROS'

RIA •i PONTEVEDRA

RIA • VIGO

N.. SPAIN SEA SURFACE TEMPERATURE NASA GSF C 1028

Plate 2b. Same as Plate 2a, but on October 2, 1984.

changesin zooplanktonbiomass were similar to the patterns Ichthyoplankton. The six most abundantfish larvae of bacterialabundance and productivityon both transectsA composed82% of the total catch. They includedGobiidae and CV. (32 %), the sardine,Sardina pilchardus (18 %), the dragonet, Nauplii abundanceswere higherat inshorecompared with Callionymuslyra (12 %), the scaldfish,Arnoglossus laterna offshorestations (Figure 16b). Nauplii abundancesexhibited (10 %), Labridae (6 %), and the anchovy, Engraulis en- a similar trend as zooplanktonbiomass on transectCV. At crasicholis(4 %). Mean abundancesof fish larvae were 20 station CV2 the nauplii remainedfairly constantover the 100 m-3, reflecting the summer spawning activity in thearea. time seriessampling, whereas there was a strongincrease in Transectswere repeated every 2 or 3 days to determine nauplii(3 to 12 ind L-1) at stationCV4. temporalvariability in responseto upwelling and/or trans- Weight-specificzooplankton grazing ranged from 26 to port. Minimal temporal variability was evident in the fish 894 mL mgC-'h 4. Grazingrates were highest at the inshore larvae samples,partly becauseof high inherent sampling stations. Similar to biomasschanges, water column clear- variability and partly becausethe timescale required for ance rates (Figure 16a) showedthe greatestincrease over detectablechanges in the compositionand abundanceof fish time at stationA4, little changeat stationsA2 and CV2, and larvae is longer than for bacteria, phytoplankton,and a slight increasetoward the end of the time seriessampling zooplankton,which have relatively short responsetimes to at station CV4. Expressedas a daily consumptionof changesin the ecosystem. Temporal responsesto changes phytoplanktonbiomass, maximum rates at stationA4 were in upwellingwould have been most evident for egg stagesof approximately100 % and at CV4, approximately26 %. ichthyoplankton,but no sardineeggs were taken. TENORE ET AL.- OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,957

0.14 (Figure 20). This patternof surfacepigments contrasts with the image on July 30, 1985, when the winds were upwelling _ ...:EThymidineBacterial AbundanceIncorporation favorable and the region of enhancedpigment concentration 0,12 was quite broad. The Arosa transecttemperature section on September 1984 March 23 (Figure 19) suggestsupwelling in the layersbelow 0.10 80 m. Salinity profiles indicatea low-salinitylayer off the Rias Bajasextending 20 to 30 km offshoreand reachingdepths of =. 0.08 40 m. The source of this water must have been the rivers of the Rias Bajas. The SW winds, which would induce a 0.08 southwardflow, appearedto constrainthis water south of Cape Finisterre. The surface salinity map (Figure 20) suggeststhere was a southwardflow in the upper water 0.04 column layers. The extent and depth of this low-salinity layer suggestsmixing related to the strongsouthwest winds 0.02 was intense. The salinity distributionalso correlateswell with surfacepigment distributionfrom the CZCS. Phytoplankton. Some measurementswere made at 0.00 _1-1 Vigo Arosa Villano Ortegal stationsC2, C4, CV2, CV4, A2, and A4. Highest rates of primary productionwere at A4 and CV2, showingno clear Figure 11. Bacterialgrowth rates estimated by instanta- trend between coastal and offshore stations. At eight neousthymidine incorporation (1- to 2-hourincubations) and stationsalong either the Coruna or Cabo Villano transects, by dilutionculture (change in bacterialabundance over 0 to chl a andprimary productionaveraged (n = 8 stations)41 mg 24 hours)techniques. Values are averagesof all stations acrosseach transect(see Figure 1 for transectlocations) m-2 and 0.48 gC m-2 d4, respectively(Figure 5). The duringthe September1984 cruise. < 12-/zmphytoplankton fraction averaged73 % of the chl a and 70% of primary production. Along the Arosa transect,chl a and primary production averaged75 mg rn-2 and 1.1 gC m-2 d 4, respectively.The Althoughthere were only two transects during this cruise < 12-/zmsize fractioncontributed most of the phytoplankton there were distinctdifferences in speciescomposition of biomassand productivity. larval fish of the northern versus the western transects Microbiology. Thymidine incorporationand bacterio- (Figure17). T. trachurusand E. encrasicholiswere plankton abundanceon both northern and western shelves significantlymore abundant and mostly taken on theVillano varied over time and space. Only bacterioplanktonabun- transect,and gobies were significantly more abundant on the dance was significantly:different overall between western Arosa transect. Sardine and labrids were abundant on both versus northern shelves (Table 3). During this cruise, transects. bacterioplanktonabundance and ratesof incorporationwere Lengths of larval sardine were significantlylonger about twice those measuredin July 1985. Comparing offshoreon the Villano (CV) and inshoreon the Arosa (A) bacterioplanktonto phytoplanktonbiomass, on the western transects[see Chesney and Alonso-Noval, 1989]. Demities shelf, bacterioplanktonbiomass was 15 to 46%, and on the of fish larvae were highestinshore on the Arosa transect, northern shelf, 70% of phytoplanktonbiomass values. decreasingto nearzero at the seawardstation, but densities Phytoplanktonbiomass on the northernshelf was low during remainedhigh or even increasedoffshore on the Villano this time series. In terms of production,bacterioplankton transect,indicating offshore transport of fish larvaeoff Cabo Villano. productionwas only 1 to 10% of phytoplanktonproduction above 15 m and equaled phytoplanktonproduction below Distinct species-specific onshore-offshore patterns 15 m water depth. occurredas well. On the Villano transectsardines, gobies, and labrids were all most abundant at the outermost station Zooplankton. Zooplanktonbiomass was the highestof all the cruises(Figure 7). Zooplanktonbiomass did not of the transect(Figure 17). On the Arosa transectthese showany patternof increaseor decreaseduring the cruise. specieswere most abundantat the inshorestation of the On the western shelf there was a nearshore band of lower- transect(Figure 17). salinitywater that had high chl a concentrationsrelative to the shelf waters; for stationson the various transectsin this Spring1986 (Cruisedates, March 22-April 2): zone the ratio of zooplanktonat 0- to 50-m and 50- to 100-m PrevailingDownwelling Conditions waterdepths averaged 4.6 at stationA4, 2.2 at stationCV4, PhysicalOceanography. Strong SW winds(Figure 18) and 1.9 at station C4. createdmoderately strong downwelling-favorable conditions Total microzooplanktonabundances were at leasttwofold for most of the cruise. Hydrographyindicated 12 to 13øC higher than on all the other cruises. The abundancesof surfacetemperatures throughout the areas. We detected copepodnauplii ranged from 3 to 47 naupliiL 4, with the little thermal structurewith depth and conditionsdid not highestabundances found at stationA2 (Figure 8a). Bivalve suggestany upwellingin the area (Figure19). This is larvaewere mostabundant (maximum of 6 ind L4) at station supportedby CZCS imagery(not shown) on April 3 which A4 in surface waters nearshore the mouth of the Ria de showsa narrow band of enhancedpigment concentrations Arosa. along the entire coast southof Finisterresimilar to the Zooplanktongrazing rates were similarover all transects. patternof lower-salinitywater along the samewest coast Weight-specificgrazing rates ranged from 10 to 118 mL 10,958 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

4000 1985 Upwelling Index - West Coast

2000 500jUpwellingIndex -1985/• O'West Coa••,••/ ••/./•.•

-500

c•.-2ooo -1000

-4000 -1500

-2000 • • • • i • • -6øøø'"Jan'Feb'Mar'Apr'May' Jun'Jul 'Aug'Sep'Oct'Nov'Dec' 27 29 31 2 4 6 8 4000 1200 1985 Upwelling Index - North Coast I / NorthCoast ,ooo I I // -2o0o

4OO • -4000

-6000

-8000 an'Feb'Mar'Apr'May' Jun'Jul 'Aug'Sep'Oct'Nov'Dec' -20027 29 3! 2 4 6 8 Jul I Aug Figure12. Calculatedupwelling indices for the (top) west and (bottom) north coasts ofNW Spain during 1985 and specificallyduring the summer1985 cruise.

mgC-i h-1, with the highest grazing rates at CV4 (Figure 8b). transectsA and C (Figure21). Comparingjust nearshore Watercolumn clearance rates were low comparedwith the stations,fish larval densities were highest on transectV. othercruises (1 to 6 L m-3 h-i). Thus the maximumzoo- Relatively few sardineeggs and larvae were taken planktongrazing rate was equivalem to a dailyremoval rate [Chesneyand Alonso-Noval, 1989], especially considering of approximately14To of thephytoplankton standing crop. thatFebruary through May is thepeak spawning time for Ichthyoplankton.Transects were repeatedlysampled sardinesin thisregion. Nevertheless,sardine eggs were every 2 or 3 days to determinetemporal variability in more abundantthan on any of the other cruisesbut were responseto upwellingand/or transport. Again, no clear-cut foundprimarily on inshorestations on transectC. Sardine patternof temporalvariability was evident in fisheggs and larvaeaveraged 4.9 mmSL andwere small compared with larvae. Thesix most abundant fish larvae composed 81% of those taken on other cruises. the total catch. They includedGadidae (47%), Gobiidae (14%), the sardine,$ardina pilchardus (11%), Labridae Discussion (6%), Blennidae(4%), and Ammodytesmarinus (3 %). Timescalesof BioticResponses to EpisodicUpwelling Meanabundances of fish larvae were 35 100m -3, reflecting Events a peak spawningtime for several speciesin the area. Nearshore-offshoredensity distributions clearly indicated It is well known that bacteria,phytoplankton, and highestconcentrations of fish larvae inshore and decreasing zooplankton generally respond to thephysical and chemical significantlyseaward (Mann-Whitney U test,p=0.05) on changes,especially nutrient enrichment,associated with TENORE ET AL.. OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,959

o

lOO

•oo- ß 11,5 - 11.5 -- -- '" 300- AROSA 1 I 30July 1985 _ 29 July 1985 400 - II Tempersturel i I - NitrateI 500 I I I I

100-" 12 .-.11,5 - o 300 I WL_LANO4__ AROSA 5 '•• 200 t _-.--11,5/...• 3August ___1985 6 Aug 1985

4001500• _-11-/ 45 30 15 0 45 30 15 Distance (krn) Distance (krn) Figure 13. Changesin temperature(degrees Celsius) and nitrate (-NO3) distributions along the coastof NW Spainoff (left) Villanoand (right) Arosa during the summer1985 cruise. SeeFigure 1 for transect and station locations.

A CaboVillano Transeot ArosaTranseot episodicupwelling eventson timescalesvarying from hours N, Coastoff Finisterre W, Coast off Rlas BaJas 18 to daysto weeks. For example, the time seriessampling off the Galician shelf showedthat bacterioplanktondemities and 17 productionincreased two to three times within 10 days of

16 36,0 the onsetof an upwelling event, but zooplanktonand fish larvae showed little change. Becauseof these different G' 15 35.5 responsetimes, a set of observationscollected on cruises 8hell Break 8tatIon CV2 8hell Break 8tatIon A2 such as these FOG studiesare, in reality, a point-of-time I I I I I I I I I I I I 35.o• "snapshot"ofthe planktonic community structure andrate E 17 :_•functions at a givenpoint of timein a dynamiccontinuum. • Thuspreceding hydrographic conditions and biotic fluxes are 36.0

Cabo Villano Transect Arosa Transeot N. Coast off Finisterra 0.10 W. Coastoff Rias BaJas Coastal Station CV4 Coastal Station A4 Shelf Break Station CV2 ' ' 35,0 0,08 ShelfBreakStatio• 0,06 6 8hellBreak 8tatIon CV2 8hellBreak 8tatIon A2 0,04 / .c • Primaryproduction • 4 0,02

0 I I I I I I I I I Coastal Station CV4 Coastal Station A4 • o ...... 0.80 • • •, Coastal8tatIonCV4 4 • 0,60 0.40

.e- 0,20 [H ß BacteriaProductionl 0 / i i ! i i i 0 I I I 27 •9 :•1 • •, • • 29 31 2 4 6 8 27 29 31 4 6 8 July August July August July August July August Figure 14. Time serieschanges in (a) temperatureand Figure 15. Time serieschanges in bacterialnumbers and salinityand (b) chlorophylla andprimary production at sta- thymidine incorporationrates along the north and west tionsA2, A4, V2, and V4 alongthe coastof NW Spain. coastsof NW Spain during the summer1985 cruise. See SeeFigure 1 for transectand stationlocations. Figure 1 for transectand stationlocations. 10,960 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

Table 2. ThymidineIncorporation and BacterioplanktonCounts Under UpwellingConditions During the Summer 1985 Cruise off NorthwestSpain

Thymidine,pmol L '• h'• Bacteria,108 cells L -•

Minimum Maximum Mean Standard Minimum Maximum Mean Standard Deviation Deviation

Shelf Northern 0.10 6.20 2.73 1.49 1.7 8.5 4.8 1.8 Western 1.10 10.10 5.78 2.79 1.0 10.2 4.6 2.3

Section Arosa 1.10 10.10 5.78 2.79 1.0 10.2 4.6 2.3 Villano 0.10 6.20 2.73 1.49 1.7 8.5 4.8 1.8

Area Nearshore 1.70 10.10 5.08 2.92 2.1 7.5 4.4 1.4 Midshelf ND ND ND ND 1.0 9.4 4.5 2.3 Outershelf 0.10 9.00 3.69 2.43 1.4 10.2 5.0 2.3

All "shelf" valuesare averagedover entire shelf. All "section"values are averagedacross each section. Mean values are for each area for both sides. ND indicates no data.

Shelf Break Stations Coastal Stations neededto understandthe nutrientand standing stock levels A, 120 N.Coast offFinisterre W.Coast offRiss Betjam describedby a setof cruisedata taken from any given point Shelf Break StationCV2 Shelf BreakStation A2 inoftime plankton andtoin interpret areas such physiologicalas the NWand coast biomassof Spainresponsesthat exhibitepisodic upwelling. Furthermore, observed spatial changesreflect not only biotic fluctuations, butalso distri- butionalchanges caused by vertical/horizontalwater mass movements.Evenspatial time series sampling isdifficult to interpretbecause of watermass movement and because more I• o intensivestudies follow plankton dynamics occurring in '.• CoastalStation CV4 StationA4 ; -••' •o Biornassl "%.-- ,, •o :• watermasses. I- "• GraZingI '....o.; . II- 0 - 'm a...•_• •. -0m 0m Others /--'..-'

27July29 31 2 August4 (5 8 July2931 2 August4 (5 8 Scale- ;•f 100m 3 •__• ',abo Ortega]

ß .

ß .

ß

.. B, 21 "/ ß LA CORUNA

• A2 • •,1, •_+-,--,---{-i-'r"',-•A2,,I S ,•%.•,Finisterre cv ; ' 'i:"'

• \ Riade Muros 'RIAS BAJAS' • 'deArosa

July August --- Ria do Pontevedra

Figure16. (a) Timeseries changes in zooplanktonbiomass F:'.'-'' de Vigo (milligramsCarbon per cubicmeter, solid lines) and water / :;. o 25 50 columnclearance rates (liters filtered per cubicmeter per Summer 1gas I ! i ß VIGO hour,dotted lines) in surfacewaters at stationsA2, A4, V2, km andV4 alongthe coast of NW Spainduring the July/August 1985cruise, (b) Time serieschanges in naupliiabundance Figure 17. Larvalfish densities ontransects A and V along (individualsper liter) in surfacewaters. thecoast of NW Spainduring the summer1985 cruise. TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,961

1986 UpwellingIndex - West Coast 4000 2001WestCoast i E ,,,,i ,._ k. • 0 -2000I x -4000•.-

.c_-4000 I • -6000 - I I I

I I I I I -- I I -8000 - I I -8000 I I

I I I I I ...... -ooo I 23 25 27 29 31 I 10000r 1986 UpwellingIndex - North Coast Upwelling Index - 1986

North Coast 21 4000 5000

2000 --

_ •

c•-5000 ._c_ -20OO --

-4000 --

-10000 I -6000 i • • • • • - 15000•,Jan 'Feb'Mar' Apr 'May' Jun' Jul 'Aug'Sep'Oct' Nov'Dec' 21 23 25 27 29 31 2 Mar i Apr Figure18. Calculatedupwelling indices for the (top) west and (bottom) north coast of NW Spainduring 1986 and specificallyduring the spring1986 cruise.

Upwellingconditions prior to andduring the June 1984 the westerncoast. Nitrateand phytoplankton decreased and cruiseresulted in highphytoplankton biomass and productiv- temperatureincreased off the northerncoast; nitrate and ity. For example,chl a andprimary production in the phytoplanktonincreased and temperature decreased off the Galicianupwelling system attained levels comparable to westerncoast. In contrast,bacterial abundance and produc- those observedin the northwestAfrica upwelling system tion increased off both northern and western coasts. These [Huntsmanand Barber, 1977]. However,both zooplankton results could be variouslyinterpreted: (1)off the western biomassand fish larvae were low during this cruise. In coast,as a responseto enhancedphytoplankton production; contrast,downwelling conditions prior to and duringthe (2) off the northerncoast, as a responseto increased March/April1986 cruiseresulted in low phytoplanktontemperature; or (3) asdue to differentbacterial populations biomass. However, we found the highestdemities of associatedwith differentwater masses. Similarly, zooplank- zooplanktonand fish larvae. Thismismatch of autotrophton datafrom thistime seriessampling illustrate the classic andheterotroph can result from both advection as well as responseto episodicupwelling enrichment to tile water differencesin responsetimes to upwellingevents. columnplanktonic community. The weakupwelling event The time seriessampling during the July/August1985 off the westerncoast brought newly upwelled water to the cruise can be used to unravel some of these phenomena. surface and resulted in decreasedzooplankton biomass. Priorto thecruise, upwelling conditions existed on boththe However, within 1 week, in responseto enhancedphyto- northernand westerncoasts (Figure 12). Downwelling planktonbiomass and production(Figure 15), increased conditionsexisted during the beginningof the cruise;a zooplanktongrazing (Figure 16), andproduction (as evi- strongupwelling event occurred on July 31 off thenorthern dencedby highernauplii abundances) had resultedin coastand a weakupwelling event occurred on August 3 off increasedzooplankton biomass. 10,962 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

O (:::) Surface Salinity I I ../ I I I I.._ I April 1986 ...... 12.7 ---- __

Ortegal

ß . /--' H ! I / /'"'--"'" 35.6-"-'-.. ß-. \ ! // lP.g _--. /t i / / /•-'""' CORUNA 35.5 ""-' ,. 35.4 .... \ • / •,.-'-'-' ._._,.•, // ;abo•illano

ß

ß ß \ \ / / / .,-"' _,- / ß • -120 I Finisterre i ....• '•...... •"-•//';'"/ / / .. -."... • • -- x / / / x /- Temperature -160 '--,. '"------'- •///_• / ArosaTransect I%t Ria•e Muros x-,. •.• "•//, •"/ 23Mar 1986 .'. .' "RIA$ BAJA$' Ri•'deArosa I •',1 ,'.. '.

ß• de Pontevedra

'"-..•,, •---"/ /,.--- 35.•"--• ...... ci•woo

35i4•I ::.. \ • [ •x • I /------"--,. '"'"--"'' VIGO \ • •,-•5.4 / / I ! x \ -.,...--" ""-• / I I IO Figure 20. Surfacesalinity contours along the coastof NW Spainduring the spring1986 cruise. r• -120- ! / I

-160 - '-_ _ _ .. /'• Salinity During upwelling conditions (summers of 1984 and / 1985), phytoplanktonbiomass and productivitywere high in responseto the nitrate input in the euphoticzone. Size -200 ; • 23MarI 198e fractionationstudies suggest that new nitrogensupported the -50 -40 -30 -20 -10 0 growthof netplankton(> 12/zm, primarily diatoms)in early Distance(km) summer1984. In early fall 1984, whenupwelling was weak Figure 19. (top) Temperatureand (bottom)salinity depth following a strong downwelling period, phytoplankton profileson the Arosa transecton March 23, 1986, during biomass decreased from that measured in the summers of the spring1986 cruise. SeeFigure 1 for transectand station 1984 and 1985, and the size structureof the planktonshifted locations. from netplanktonto nanoplankton(< 12 /zm). This shift suggestsa change to alternate nitrogen sources, e.g.,

Table 3. ThymidineIncorporation and BacteriaCounts Under DownwellingConditions During the Spring 1986 Cruise off NorthwestSpain

Thymidine,pmol L -• h'• Bacteria,108 cells L -I

Minimum Maximum Mean Standard Minimum Maximum Mean Standard Deviation Deviation

Shelf Northern 0.90 18.20 6.57 4.11 5.1 10.2 7.2* 1.3 Western 0.84 58.82 9.00 9.88 5.9 14.5 9.5* 2.2

Section Arosa 0.84 59.82 9.00 9.88 5.9 14.5 9.5 2.2 La Coruna 1.10 14.96 6.18 3.71 5.1 10.2 7.6 1.3 Villano 0.90 18.20 7.02 4.55 5.2 8.5 6.6 1.0

Area Nearshore 1.59 18.13 6.49 3.55 5.8 12.1 7.8 1.6 Midshelf 0.84 18.07 6.89 4.53 5.5 11.1 8.2 1.7 Outer Shelf 0.90 59.82 9.34 10.90 5.1 14.5 8.2 2.7 All "shelf"values are averagedover the entireshelf. All "section"values are averagedacross each section. Mean values are for each area for both sides.

*Significantdifferences are at the 99% confidencelevel (studentt test)between means. TENORE ET AL.. OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,963

Previous work [Blanton et al., 1984] showed that surface - 50 I• sardine • Gadidae ., waters in the rias advect seaward when NACW intrudes into I--I otherlarvae the rias as a subsurfacelayer. These intrusions occur Scale-per 50 m 3 • ..// throughoutthe upwellingseason and are a primary sourceof fo nutrientssustaining the high productionoff the rias [Campos Ortegal and Gonzalez, 1975]. However, Alvarez-Salgado et al. [1993] discussthe potentialcontribution of mineralizationof organic matter outwelling from the rias contributingto the

LACORUNA nutrient pool of the shelf waters. Mixing of intruded ß NACW with the lower-salinity waters in the rias occurs in ß' •:' ß. . ( 'Cabo'•iilano the middle and inner Ria de Arosa [Hanson et al., 1986]. • ,.', This mixing of nutrient-rich intruded water into the photic • .... . [ Finisterre zone results in high primary production. The resultant ! ! :.". phytoplanktonbiomass of typically estuarinespecies in the t I ' - rias is advectedseaward. Both zooplanktonand fish fauna • ...ß near Arosa are more typical of the rias than speciesfound ( Ria;:le Muros .'. on the northern transects. Fish species more typical of ß:.. 'RIAS BAJAS' %• .. classicupwelling systems are seenin the north, while in the • de Arosa south, large numbers of gobies and labrids indicate more • '.. -. •2',,I• . . coastal estuarine influence. Similarly, the zooplankton r=_ ] • Riade Pontevedra communityon the westernshelf containsseveral species of invertebrate larvae which are outwelled from the rias. / •, •iade vigo .'. 0 25 50 Effects on Fisheries Along the Galician Shelf Spring1986 WGO km Temporal distributionand abundanceof fish eggsduring Figure 21. Fish larval densitiesalong the coast of NW the four cruisesreflected seasonal spawning patterns; spatial Spain during the spring 1986 cruise. distributionof sardineeggs and larvae reflectedthe distribu- tion of the spawningadults and the patternof oceanographic currentswhich dispersedthe eggs and larvae. Acoustical surveysof sardineshave shownthat adultsgenerally distrib- ammoniumfrom nitrogen regeneration,was supporting ute themselvesand spawn close inshore along the Galician continuedphytoplankton growth. Duringthis weakupwel- shelf [see Garcia et al. 1988, and references therein]. ling period in the fall 1984 cruise, zooplanktonbiomass However, in our study the sardine larvae tendedto be just exceededphytoplankton biomass. During downwelling as abundantand larger offshoreas inshore(Figure 23). This conditionsin the spring 1986 cruise we also found low suggeststhat during upwelling-favorable periods, larvae phytoplanktonand high zooplanktonbiomass. were transportedoffshore from inshore spawning sites. On the other hand, the effect of precedingand current Sardine abundances,length frequencies, and the likely hydrographicconditions on the bacterioplanktonwas not at pattern of coastalflow [McClain et al., 1986) suggestthat all obvious from these studies of short duration because larvae were dispersedwestward and offshorenorth of Cape bacteriacan correlate with both related changes in phytopla- Finisterre. Southof Cape Finisterre,fish larvae appearedto nkton and zooplankton. High bacterioplanktonoccurred be dispersedto the southand offshore. alongwith high phytoplanktonbiomass in the summer1984 The highly productiveconvergence zone of two water cruise but not in the summer 1985 cruise. Because of their massesjust north of Cape Finisterre occursoffshore from short generationtimes, bacteriacan respondrapidly to the coastal upwelling [Fraga, 1981; Fraga et al., 1982; increasesin bothphytoplankton and zooplankton. Enhanced Estrada, 1984; McClain et al., 1986). Adult sardines are phytoplanktonproduction, with accompanyingleakage of known to concentrate inshore, so the observed higher dissolvedorganic substrates, can resultin increasedbacterial concentrationsof sardinesand other ichthyoplanktonoff- productionand biomass[e.g., Duursma, 1961]. Increases shore in June 1984 and July 1985 (Figures 9 and 18) must in bacterialbiomass and productioncan also result from a havebeen due to offshoretransport and concentration caused greater release of dissolvedorganics associatedwith in- by the frontal convergence. The fish larvae collected creasedzooplankton grazing [Romanet al., 1988]. offshore also tended to be larger/older larvae. In contrast, in March 1986, when downwellingconditions prevailed, no MesoscaleSpatial and Temporal Patterns in the Galician sardine, but other fish larvae, were observed at the offshore Shelf Coastal Systems stationsnear the convergencezone (Figure 21). Winds in Superimposedon macroscaleatmospheric and oceano- March 1986 were strongand variable, shifting from down- graphicpatterns are mesoscaleupwelling/downwelling due welling to upwelling favorable during the cruise, and the to coastaltopography and outwellingfrom the rias (Fig- water column was mixed. Strong turbulent mixing is ure 22). Surfacesalinities nearshore the rias duringthe June generally believed to be detrimental to survival of early campaignwere less than expectedfrom T/S relations of stage fish larvae [Lasker, 1981; Peterman and Bradford, North Atlantic Central Water (NACW). Seawardadvection 1987; Cury and Roy, 1989]. Given that March is one of the of low-salinitywaters from the rias is a likely explanation peak spawningperiods for sardines,there were surprisingly for the reducedsalinities nearshore off the Rias Bajas. low numbersof sardineeggs and larvae along the Galician 10,964 TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN

TYPICAL SPRING-EARLY SUMMER UPWELLINGPATTERN WITH NE WINDS

OUTWELLING ESTUARINE WATER OVERLAYS SUBSURFACE UPWELLED WATER UNLESS SUBSEQUENT STRONG SE WINDS OFF THE RIAS BAJAS ENHANCE NORTHWARD MOVEMENT OF FRESHWATER. e.g. JUNE 1984 and MARCH 1986 SURVEY

TYPICAL LATE SUMMER-EARLY FALL UPWELLING PATTERN.

SURFACE UPWELLING OCCURS ALSO ALONG THE COAST OFF THE RIAS BAJAS WHEN LOWER PRECIPITATION RATES RESULT IN LOWER OUTWELLING OF ESTUARINE WATER. e.g. SEPTEMBER-OCTOBER 1984 SURVEY

Figure22. Diagramillustrating the effects of coastaloutwelling on upwelling along the inshore western coastof Galicia, NW Spainoff the Rias Bajas.

coast at that time; this absencesuggests that either little The Iberian stock of sardines has not shown wide fluctua- sardinereproduction had occurredor sardineegg andlarval tionsin catchnor apparemsteep population declines typical survivalin the area prior to the March cruisewas poor, of many upwelling fisheries. Of course, sardine and perhapsas a result of strongmrbulem mixing. In either anchovycatches from this Galician fisheriesare 2 orders of casethere would have been little opportunityfor advection magnitudelower than that of Peru. Annual catchdata from of sardinesand other larvae offshore as wasobserved during the Atlantic Spanishcoast (FAO area 27) since 1980 have periodsof moderateupwelling. rangedfor anchoviesbetween 0.01 to 0.12 and for sardines TENORE ET AL.' OCEANOGRAPHY OFF GALICIA, NW SPAIN 10,965

lOO R. Pomeroy and J. J. Alberts, pp. 171-193, Springer-Verlag, New York, 1988.

.:.:.:.:.:.:.:.:.:.:.: :::::::::::::::::::::: Blanton, J., L. Atkinson, F. De Castillejo, and A. Montero, >;.:.:.:.:.:.:.:.:.:. 80 ' '"'""'"':•Eggs Coastalupwelling off the Rias Bajas, Galicia, NW Spain, I, Hydrographicstudies, Rapp. P.V. Reun. Cons. lnt. Explor. •L•rvae Mer., 183, 79-90, 1984. õ oo Blanton,J. O., K. R. Tenore, F. Castillejo, L. P. Atkinson,F. B. Schwing,and A. Lavin, The relationshipof upwellingto mussel productionin the rias on the westerncoast of Spain, J. Mar. ß 40 ...... Res. 45, 497-511, 1987. .=_ Campos,M. J., and N. Gonzales,Phytoplankton in relationwith nutrientconcentrations in the ria de Arosa, in Proceedingsof the 10th European Symposium on Marine Biology, Ostende, =o Belgium,Sept. 17-23, vol. 2, pp. 111-125, 1975. Chesney,E. J., and M. Alonso-Noval,Coastal upwelling and the 0.15 • 15- 30 I 30- 50 early life history of sardines(Sardina pilchardus) along the Galician coastof Spain, Rapp. P. V. Reun. Cons. Int. Explor. Distancefrom coast (km) Mer. 191, 63-69, 1989. Cury, P., and C. Roy, Optimalenvironmental window and pelagic Figure 23. Percentof the total sardineeggs and larvae fish recruitmentsuccess in upwellingareas, Can. J. Fish Aquat. capturedrelative to stationdistance from the coast. Data are Sci. 46, 670-680, 1989. a compositeof all stationsalong each transectand all Daro, M. H., A simplified14C method for grazingmeasurements cruises. on naturalplanktonic populations, Helgo. Wiss.Meeresunters., 31, 241-248, 1978. Dugdale,R. C., and J. J. Goering,Uptake of new and regenerated formsof nitrogenin primaryproduction, Limnol. Oceanogr.12, between0.06 to 0.10 million t. In comparison,annual catch 196-206, 1967. Duursma,E. K., Dissolvedorganic carbon, nitrogen, and phospho- data for the Peruvian upwelling system since 1973 have rous in the sea, Neth. J. Sea Res. 1/2, 1-147, 1961. rangedfor both anchoviesand sardinesbetween 2 to 4 mil- Estrada,M., Phytoplanktondistribution and compositionoff the lion t. The low values of anchovies for the Galician coast coastof Galicia(northwest of Spain),J. Plankton.Res. 6, 417- mightbe becausethis regionrepresents the southernlimit on 434, 1984. the range for this species. In fact, anchovydata along the Fraga, F., Upwelling off the Galician coast, noahwestSpain, in Portuguesecoast are consistentlyminimal (<0.01 t). CoastalUpwelling, Coastal Estuarine Sci., vol. 1, editedby F. A. Richards,pp. 176-182, AGU, Washington,D.C., 1981. The NW corner of the Iberian peninsulaappears to be an Fraga, F., C. Mourino, and M. Manriques,Las masasde aquaen importantarea for the Iberian stock of sardines,sometimes la costade Galicia:Junio-Octobre, Result. Exp. Cient., 10, 51- holding a large fraction of the total stock in a relatively 77, 1982. small area [Pastor et al., 1986a, b]. Becauseof the unusual Fuhrman, J. T., and F. Azam, Thymidine incorporationas a geometryof the particularupwelling region [McClain et al., measureof heterotrophicbacterioplankton production in marine surface waters: Evolution and field result, Biol. Morya 1986], the persistenceof the upwellingassociated with the Vladivostok, 66, 109-120, 1982. NW corner of Iberia may provide a regional stability in Garcia, A., C. Franco,A. Sola, M. Alonso, andJ. M. Rodriquez, primary and secondaryproductivity. This, in turn, may Distributionof sardine (Sardinapilchardus Walb.) egg and promote a greater stability in the local fisheries than is larval abundancesoff the SpanishNorth Atlantic coast(Galician typical of many upwelling regions. andCantabrian areas) in April 1987,Rep. H:21, Int. Counc.for Explor. of the Sea, Copenhagen,1988. Glibert, P., and T. Loder, Automatedanalysis of nutrientsin Acknowledgments.We wishto thankthe manypersons who seawater:A manualof techniques,Tech. Rep. WH01-77-47, havehelped during this work. This researchwas funded by the WoodsHole Oceanogr.Inst., WoodsHole, Mass., 1977. U.S.-SpanishJoint Committee for Technical and Scientific Coopera- Gordon, H., D. Clark, J. Brown, O. Brown, R. Evans, and W. tionand the SpanishInstitute of Oceanography.The captainand Broenkow,Phytoplankton pigment concentrations in the Middle crewof the R/V Cornidede Saavedraprovided cooperation and AtlanticBight: Comparisonof ship determinationsand CZCS helpat sea.We thankFrank Kinnelly, who as scienceattach6 at estimates,Appl. Opt. 22, 20-36, 1983. the AmericanEmbassy, was instrumental in programencourage- Hanson,R. B., M. T. Alvarez-Ossorio,R. Cal, M. J. Campos,M. mentand funding. We alsothank Jeronimo Corral of the Spanish Roman, G. Santiago, M. Varela and J. A. Yoder, Plankton Instituteof Oceanographyfor his steadfastand energetic support responsefollowing a springupwelling event in theRia de Arosa, andadvice throughout the project. We wouldlike to offerspecial Spain, Mar. Ecol. Prog. Ser. 32, 101-113, 1986. thanksand gratitude to LuisLosada Lago of Villagarcia,who has Hobbie,T. H., R. T. Daley, andS. Jasper,Use of nucleporefilters beenthe single most important impetus during all theyears of this for countingbacteria by epifluorescencemicros-copy, Appl. program.He, alongwith the many Gallegosin Villajuanand Environ. Microbiol. 33, 1225-1228, 1977. Viiigarcia,have provided support, advice, humor, and f{iendship. Huntsman, S. A., andR. Barber,Primary production off northwest Thispaper is ContributionNumber 2641, Centerfor Environmental Africa: The relationshipto wind and nutrientconditions, Deep andEstuarine Studies of theUniversity of Maryland. Sea Res. 24, 25-33, 1977. Jury,M.R., Casestudies of the responseand spatial distribution of References wind-drivenupwelling off the coastof Africa: 29-34 degrees South. Cont. ShelfRes. 8, 1257-1271, 1988. Kirchman, D., H. Ducklow, and P. Mitchell, Estimatesof bacterial Alvarez-Salgado,X. A., G. Roson, F. F. Perez, and Y. Pazos. growthand biomass,Appl. Environ.Microbiol. 44, 1296-1307, Hydrographicvariability off the rias Baixas(NW Spain)during 1982. the upwelling season,J. Geophys.Res. 98, 14,447-14,455, Lasker, R., Factorscontributing to variablerecruitments of the 1993. Northernanchovy (Engraulis mordax) in the Californiacurrent: Barber,R. T., Oceanbasin ecosystems, in Conceptsof Ecosystem Contrastingyears, 1975-1978,Rapp. P. V. Reun. lnt. Explor. Ecology:A ComparativeView. Ecol. Stud.vol. 67, editedby L. Mer. 178, 375-388, 1981. 10,966 TENOREET AL.' OCEANOGRAPHYOFF GALICIA, NW SPAIN

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