Spatial distribution in winter of the primary productivity in the Ria of Pontevedra (NW of Spain), is shown. It is proved that industrial and urban efluents have a negative effect on photosynthesis, especially on the surface of the water, and on the Northern Coast, which is in accordance with the dynamics of the RiaOn indique la distribution spatial d'hiver de la production primaire dans la Ria de Pontevedra (NO d'Espagne). Les debuts industrielles et urbains affectent negativement la photosynthése. Cette influence est plus noté dans la surface et spécialement dans la zone Nord de la Ria

Cabanas-López, J.M. (José Manuel)

González, J.J. (Juan José)

González-Quijano-Mosteiro, A. (Amelia)

English

Repositorio Institucional Digital del IEO

"This paper not to be cited without prior reference to the author"INTERNATIONAL COUNCIL FOR THEEXPLORATION OF THE SEA.C.M. 1982/L:54BIOLOGICAL OCEANOGRAPHY COMMITTEEID'. MARJ:t-E~ Q.W..I1Y ~"PRIMARY PRODUCTIVITY IN \IIINTER IN THE RIA~F PONTEVEDRA {NW.OF SPAIN) AND THE CHANGESCAUSEDBY THE CONTAMINATION"J.J. GONZALEZ*, J.M. CABANAS**, A. GLEZ-QUIJANO** Instituto Español de OceanografíaCentro Costero de VigoAvda. Orillamar, 47VIGO (ESPAÑA)**Instituto Español de OceanografíaCentro Costero de La CoruñaApartado, 130LA CORUÑA (ESPAÑA)ABSTRACTSpatial distribution in winter of the primary productivity in the Riaof Pontevedra (NW of Spain), is shown. It is proved that industrial andurban efluents have a negative effect on photosynthesis, espe-cially on the surface of the water, and on the Northern Coast,which is in accordance with the dynamics -o~ th~ Ria.RESUMEOn indique la distribution spatial d'hiver de la production primairedans la Ria de Pontevedra (NO d'Espagrte).Les debuts industrielles et urbainsaffectent negatii'vementla photosynthése. Cette influence est plus noté dansla surface et spécialement dans la zone Nord de la Ria..:1 N T R O D U e T IONThe Ria of Pontevedra (or Marin), is one of the four "Rias Bajas"of'Galicia, situated in the NW of Spain (Fig. 1).lt has the following characteristics in common with the other fourRias: a) NW/SW orientation of the central axis. b) Positive estuarial cir-culation (Parthy due to the fact that the largest rivers that run into theRias, do so in the innermost section). c) Upwelling phenomena (produced byNW winds in the next platform, and perhaps the influence of deep water fromthe Mediterranean). d) The2 have an owerage depth of 20-30 m., with surfaceareas of between 130-240 K , varying in length from 18-33 Km. e) Semidiurnaltide cycle with tidal variation between 1,5 and 4 m.As a consequence of the above, and of its geographical positi~n theRias have a high primary productivity (with values of up to 2,0 grC/m day)which gives rise to intensive semiculture of mussels, and the existence oflarge natural banks of clams, oysters, cockles, scallops, razorshell, andother crustaceans and mollucs.The Ria of Pontevedra is 23 Km. long, and has an area of 152 Km2 inthe shaded area (Fig. 1), with depths of up to 47 m. in the wider centralpart, and approximately 1 m. to the East of Tambo isla§d.The average flow of the Lerez River is 1,67 Hm , with wide seasonalvariations, and the total contribution to the Ria by natu§al streams andrun-off (including the Lerez) can be estimated at 2,75 Hm /day.The location of the principal waste outlets, of both urban and in-dustrial origin, is shown in Fig 1, and its qualitative and quantitativecharacteristics, in Table 1.The nature of sorne of these outlets (highly-coloured, strong-smelling,and foam-producing), the fact that it is a tourist zone, and the hypotheti-cal reduction in the quantity and quality of shellfish stock, brought aboutthe programming of an interdisciplinary study of this Ria. Some of the dataobtained in Phase 1 of this study, are shown in this paper.o B J E e T 1 V E.1.- Make a diagnosis of the present state of the Ria, and itsforeseeable evolution.2.- Find out how the effluents affect the biotope and biocoenosis.3.- Compare the biological/oceanographical characteristics with thetwo closest Rias (Arosa and Vigo), of which more is known.4.- Propose immediately-feasible solutions, to avoid the deteriora-tion of this area.M E T H O D O L O G Y.The study of the pollution of the Ria of Pontevedra, was divided intotwo phases. The first, which began in winter 1980, involved making a preli-minary assessment of the problem, and defining the programme of work to bedone in Phase 11.After compiling, analizing and synthesizing all existing data, a20 day long field-trip was planned, in which the principal was~te outlets were located and analysed, qualitatively and quantitatively;the marine dynamics, meteorology, microbiology, benthos, phytoplanckton andzooplanckton, hydrography, primary productivity, heavy metals, DDT's andPCB's, hydrocarbons, detergents, etc.,were studied.S A M P L 1 N G.From 15th February to 4th March 1980 samples were taken twice (se-ries A and B), from the 20 stations whose location is shown in Fig. 2. Anattempt was made to take them in differing tidal levels, but this was notalways possible.The taking of water was carried out with Niskin bottles, equippedwith inversion thermorneters. The depths were decided upon after checking thewhole water column with a RS5 (Beckman) salinometer, and an underwater photo-meter. Normally less than 10 m. of water wasleft unsampled. The nurnber ofbottles used, varied between 2-7.Samples were taken to determine salinity, dissolved oxigen, nutrients,partieulate C and N, ehlorophyls, and phytoplanekton. The primary produeti-vity "in situ" with C-14, was determined at the stations marked with a blaekdot in Fig. 2.M A TER I "A L A N D M E T H O D S.a) Solar radiation. At eaeh st.at.Lon,measurements were taken everymetre, with an underwater light meter (Kalsieo, model 268). When the ineuba-tions were eolleeted, the readings were repeated.Wit}¿ thedata the best-adjusted eurve was plotted for the equation1 = 1 x e- z, obtaining from it the values of 1 and K. From the equationwere ~lso ealeulated the theoretieal depths reaeged by 25%, 50% and 100%of the ineident radiation.b ) Nutrients. The, sarnpLes were preserved by quiek-freezing at -20 ºCin 40% glieol solution. The nutritive salts (NO;, NO;, NH~, P04H;, Si(OH)4)were determined with a Teehnieon AAII Autoanalyzer, using the Striekland andParsons method.e) Chlorophyles and other pigments. 2-3 litres of water were passedby vaeuum through Whatman GF/C filters. These were frozen at -20 ºC in een-trifuge tubes, with serew eaps, in whieh the extraetion was earried out inthe laboratory.The readings were taken using a speetrophotometer with a double beam,using cells of 5 cm. light path.The pheopigments were determined by adding C1H and taking readingsat 750 and 665 nm.The formulas used were those of Jeffrey and Humphrey and Barnes,with eoneentrations of Chlor."a", Chlor. "b", Chlor. "e", Carotenes, Xantho-phylls, Index 430/665 and Pheopigments.d) Primary produetivity with C-14. The usual teehnique of "in situ"ineubations was used, with a duration 2-2Yz hours. The depths were those atwhieh there was a light energy of 100%, 50%, 25% and 10% of the ineident ra-diation at the beginning of ineubation, the latter being performed between10 am and 13,30 pm (local time).Photosynthesis was stopped with Lugo l. The eellulose aeetate filters,had a pore size of 0,8 u.The readings were taken using a liquid seintillation.eounter (Paekardtriearb. Model 2002).8 hours of light per day were eonsidered with the graphie integra-tion earried out throughout the photie zone.R E S U L T S A N D D I S C U SSI O N.a) Light Radiation. The quantity of light energy at sea leve~ duri~gthe sampling period was low, (usual in winter), of th~ order of 65-100 W/mwith wide variations: extreme values of 8 and 550 W/m ..The absolute values of the extinetion eoeffieients, ealeulated aspreviously indieated, show some quite marked eharaeteristies:1.- They are very high in the interior part of the Ria, and de-crease towards the mouth.2.- The tides and the wind play an important roleo The highestvalues were obtained at the end of the ineoming tide, with Westerly winds.(the effluents are trapped in the interior of the Ria). Fig. 3 and 4.In eomparison with the Ria of Arosa where a river with a larger vo-lume of water than the Lerez, flows out into the most internal part of theRia, the values of the extinetion eoeffieients of the Ria of Pontevedra, are30-50% higher. This inerease is mainly due to industrial effluents.3.- The penetration of light throughout the water eolumn is lessin the Northern part, than in the South. This oeeurs from station 4 towardsthe West, and eonfirms the studies of the hydrology and dynamies, whieh in-dieate that the principal outlet of fresh water (and therefore of industrialand urban effluents) is to the South of Tambo Island, and it then flows claseto the North Coast.In Fig. 5, are shown some values of the theoretieal depth to whieh50% of the light reaehing the surfaee of the sea penetrates.b) Nutrients. Normally in the Rias, the limiting nutrient is inorganic nitro- -,gen. Phosphates are almost always present in sufficient quantity to supporthigher producti vity levels (the muddyvbot toms of the Rí.as 'act as r-egu Lat.or-s :they absorb the phosphates when they are present in high concentrations,and release them when they become scarce).The distribution of ni trates during the survey was typical for winterin the Galician Rias: at the more interior stations, there were higher levelsat the surface than at the bottom, and in the rest of the Ria, there were ve-ry homogeneous concentrations, of the order of 4-6 patg. N-NO;/l. The mainorigin seems to be from the land.c) Chlo§ophyls. The values of chlor. "a" at the surface varied from 0,2 to4 mg./m , with lower concentrations in the more interior part, and increa-sing along the central axis of the Ria, as can be seen in Fig. 6 and 7.In general terms, the largest phytoplancktonic biomass is in the ex-ternal part of the Ria (Fig. 8). This distribution cannot be totally attri-buted to the contamination, given that in the other Rias, the same occurs inwinter. Id) PrimarY2Productivity. The values found are typical of the winter season(160 ~gC/m day) although sporadically there were high values (460 and 350mgC/m day) (Table 2).These high values are due to the fact that when the incubations were~done, there was sufficient light which easily penetrated the water column(station 11 and 13). On the contrary, at station 3 and 7, where there weresimilar levels of light and nutriens, the productivity was one-third lower,fundamentally due to the poor light penetration (high K values).Station 3 is nearest to the ciutlet from the pulp and paper factbry,whose effluent, in addition to the characteristics noted in Table 1, has adeep chocolate-brown colour (aprox. 2000 colour-units Pt-Co). Most of the in-,,,,-';¡,J.dustrial and urban waste passes Station 7, mostly on the surface.Photosynthesis is carried out more rapidly in the Southern part than~ in the North, as can be seen by the data of both chlorophyl "a" and C-14.This is due to the circulation in the Ria, and location of the effluentoutlets.This North/South difference is more marked at the surface than overthe water-column as a whole. (The effluents are released at the surface, andare less dense than the seawater). If the values of chlorophyl "a" at station4 in Fig. 6 and 7 are observed, they can be seen to clearly confirm this.In Fig. 11, in which only surface photosynthesis in shown, the North/South differences are confirmed. (The exception of station 4 is due to thefact that, as previously mentioned, this is the place where most of the po-llutants of the Ria penetrate.In Fig. 12 and 13, the anomalies or deviations of the chlor. "a" va-lues at the surface, are shown in relation to the water column as a whole.The role played by the tides is confirmed.Levels of dissolved oxigen and particulate C and N reaffirm theabove.It is thought that the industrial effluents, in addition to inhibi-ting light penetration, contain chemical compounds, which reduce photosyn-thesis.I.~ J.."e~ ",'ve,...tsPAÑAFdg, 1.- Ria of Pcnt.evedr-a , Location of industrial and urban waste out l et.s..2.,0COMBARRO1-•5•O 1. TAMBO4-•6•H•8•<,i9 -.--18•H•16•1.(.,•15• 14•.JFig. 2.- Location of stations. PrimaryProduction sampling points."-.J- (). .J()Fig. 3.- Extinction coefficients (-K) (rising tide)Fig. 4.- Extinction coefficients (-K) (falling tide)-,'J.5i~.IT}l !~fÜ')'\ .IFig. 5.- Depths in metres to which 50% incident radiationpenetrates..- -,,,,--------',2I3-,--------..1 ---L 6 B 12 16 20Fig. 6.- Maximun and mlnlmun values of chorophyl "a" atsurface along the central axis of Ria.- ,- .•.. ...,,.,,.,60..-50~LO-r-30,-.,..,.-- I,o •U::l~:-"-_~ ---./-; - -- ---,--- - - -,--- -,. - -- -,- -----¡-- ----.,----T-.3 L 1:; 1::' 70Fig. 7.- yalues of Chor. "a" integrated along the watercolumn, following the central axis of the RiaIlí1 :-"rFig. 8.- Values of Chlor. "a". - - 2{integrated)mgr./m •-"J16Fig. 9.- Photosynthesis mgC/m2•day." ¡ Fig. 10~''""Chlor. "a" integrated. '(mg.•.Chlor .•"a"'¡m~)J' .3.Fig. 11.- Photosynthesis at surface (mgC/m hour),, .....~. ;::/Fig. 12.- Chlorophila "a" anomalies at surface (falling tide)Fig. 13.- Chlorophila "a" anomalies at surface (rising tide)T A B L E 1Characteristics and amounts of principal polluting discharges.Industry Suspended Dissolved (BOD)5 (COD)or Area Sol idsKg./da,y Solids Kg/day Kg. °2/day Kg. °2/dayFactory of INoodBoards 01 69 192 141 288Pulp of PaperMill O 2 5903 83440 28590 59010PontevedraO 3 3106 4401 1180 2130Marin04 324 540 131 309Bueu05 243 405 99 232PoioO 6 304 506 131 309SanxenxoO 7 101 169 41 97T A B L E .2Some primary productivity data with C-14.Station 2P .P. mgC/m day N03 in photiczone r=':-K Incident 2IN/mradiation.13 460 6-7 0,21 32011 350 4-6 0,21 28016 50 3-4 0,21 2019 78 3-4 0,22 163 105 3-4 0,44 3507 90 8-9 0,38 230

´Primary productivity in winter in the Ria of Pontevedra (NW of Spain) and the changes caused by the contamination

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´Primary productivity in winter in the Ria of Pontevedra (NW of Spain) and the changes caused by the contamination

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