Transactions on Ecology and the Environment vol 27 © 1999 WIT Press, www.witpress.com, ISSN 1743-3541 Plankton disturbance at Suape estuarine area - Pernambuco - Brazil after a port complex implantation S. Neumann-Leitao, M. L. Koening, S. J. Macedo, C. Medeiros, K. Muniz and F. A. N. Feitosa Department of Oceanography of the Federal University of Pernambuco, Campus Universitdrio, 50.679-901, Recife, Pernambuco, Brazil Abstract The plankton structure was investigated at the estuary of the River Ipojuca after 1 0 years implantation of a Port Complex. Plankton was sampled in one fixed station. Concurrent hydrological, climatological and chlorophyll a data were taken. The course of the river alteration resulted into an estuary that tends to evolves from a classical towards a coastal lagoon type. Chlorophyll a presented low values for an estuarine mangrove area. Plankton high diversity (> 3.0 bits.ind"*) can be explained by the spatial heterogeneity, although a general biodiversity decrease was registered after port implantation. Phytoplankton presented 98 taxa outranking diatoms (72 species). Zooplankton presented 63 taxa outranking rotifers (29 species) and copepods (21 species). Less than 5% of these taxa were very frequent. Irregular fluctuations in plankton densities were observed with a sharp abundance decrease after port implantation. The community was dominated by marine eurihaline species with a high proportion of littoral taxa. Meroplanktonic larval recruitment was reduced by landing and dredging. The anthropic impacts affected the system balance. 1 Introduction A Port Complex was implanted in the south coast of Pernambuco State, Noth eastern Brazil in 1979/1980 as a solution to the State economy collapse. Two years before (1977/1978), an Ecological Study Program was introduced to Transactions on Ecology and the Environment vol 27 © 1999 WIT Press, www.witpress.com, ISSN 1743-3541 48 Ecosystems and Sustainable Development obtain the general diagnosis of the area. These studies (Melo Filho\ Cavalcanti et al\ Eskinazi-Lega & Koening^, Paranagua^, Neumann-Leitao et a/7, and others) revealed a high productive balanced ecosystem and suggestions were made to minimize the impacts. After the Port implantation, ecological studies were made by the Department of Oceanography of the Federal University of Pernambuco, from 1886 to 1991; the present paper focalizes the reef area in 1990-1991 at the mouth of the River Ipojuca to assess some of the impacts and summarizes the seasonal and nyctemeral structure of the plankton dynamics. 2 Study area The Suape coastal estuarine complex is located at 8°15' - 8°30' S and 34°55' - 35°05' W, about 40 km south of Recife City (Figure 1). Climate is warm- humid, pseudo-tropical (Koppen As') with mean annual temperature 24°C and rainfall 1500-2000 mm.yr"\ concentrated from March to August. Humidity is higher than 80%. Predominant winds are from the southeast. The former Atlantic plain forest has largely been replaced by sugar cane culture (Neumann- Leitao & Matsumura-Tundisi®). Before the port implantation four rivers (Massangana, Tatuoca, Ipojuca and Merepe) converged to Suape Bay, itself an estuary partly isolated from the ocean by an extensive arenitic reefline. Today, converge into Suape Bay the rivers Massangana and Tatuoca. The Ipojuca and Merepe had their communication with the bay interrupted by intensive embankment to build the Port Complex. As a result of the weak communication with the sea, the reflow of these rivers flooded the surrounding fields causing damage to agriculture. The Government solution was a partial breakage of the reefline. In consequence a high amount of suspended material now pass through the reefline opening settling inside the Port, with a high cost dredging. In Suape area more than 600 hectares of mangrove have been destroyed (Neumann et al^). 3 Material and Methods Climatologycal data were obtained from the Usina Salgado Meteorological Station, located 5 km southwest Suape Port. Samples were collected at 1 fixed station close to the reef, in a spring tide, during consecutive 24 h, each 1 hour interval (hydrology) and each 2 hours interval (plankton and clorophyll a), in August/90 (rainy season) and January/91 (dry season). Hydrological data were collected at surface and at 1m from the bottom with a Nansen bottle. Water temperature - reversion thermometer affixed to Nansen bottle; salinity - Mohr-Knudsen method (Strickland & Parsons^); pH - Beckman Zeromatic II pHmeter; dissolved oxygen - Winkler method (Strickland & Parsons^); nutrients - (Strickland & Parsons^); water transparency - Secchi disc. For sampling the phytoplankton it was filtered 60 liters of water through a PVC pipe 30 cm high and 10 cm diameter with a mesh size 45 urn fitted in one Transactions on Ecology and the Environment Ecosystemvol 27 © 1999s WIT and Pres Sustainabls, www.witpress.coe Developmenm, ISSN 1743-3541t 49 end. For the zooplankton it was used the same methodology although the mesh size was 65 jj,m. After filtration the material of each sample was transferred to a proper flask and preserved in 4% formaldehyde-seawater solution. Phytoplankton analysis was made in an inverted microscope. Zooplankton entire samples were analysed in a Sedwick-Rafter chamber under Zeiss microscope. Chlorophyll a was collected with 1 liter Van Dorn bottle at surface and 0.1% of surface incident light intensity. Chlorophyll a was measured by Micronal B280 Spectrophotometer according to Strickland & Parsons^. Species diversity was calculated by the Shannon^ index. Persons's product-moment correlation was calculated to measure the relationships between species of all samples after a matrix of log transformed abundances (number of taxa per nf). A cluster analysis was performed using the Weighted Pair Group Method, Arithmetic Averages (WPGMA). The Principal Component Analyses was computed based in the matrix formed by planktonic taxa (> 35% occurrence), Chlorophyll a, Species Diversity and hydrological data. Standardization was performed to all data. Statistical analyses were carried out using the Numerical Taxonomy and Multivariate Analyses System - NTSYS - ver. 1.30 (Metagraphics Software Corporation, California - USA, 1987). -8"22'S -8°23'S ATLANTIC OCEAN - 8°24'S 1 35°W 34°57W Figure 1 - River Ipojuca area, Suape, Pernambuco, Brazil *A - Sampling station Transactions on Ecology and the Environment vol 27 © 1999 WIT Press, www.witpress.com, ISSN 1743-3541 50 Ecosystems and Sustainable Development 4 Results and Discussion 4.1 Abiotic dynamics The average rainfall from 1970-1990 was minimum in October (51.40 mm) and maximum in July (396.30 mm). The total annual average was 1,814 mm and the rainy season occurring from March to August. The water temperature was not a limitant factor due the narrow range of values measured. A clear minimum (26.2°C) during rainy season (July/90) and a maximum (30.0 °C) in the dry season (January/91), reflected the tropical condition of Suape area. Salinity showed an irregular pattern. At the rainy season, the surface salinity decreased from 36.41%o (5:30 h) to 11.7%o (13:30 h), rising to 36.00%o at 16:30 h followed by a decrease to its minimum of 4.17%o at 1:30 h. The bottom salinity presented a similar pattern. At the dry season, the salinity continuously oscillated up and down, both surface and bottom, with maximum at 5:30 h (37.18%o - surface; 39.04%o - bottom) and minimum of 11.15%o at 3:30 h (surface) and 21:30 h (bottom). Vertical stratification was restricted to the rainy season when a complete flushing of the estuary by freshwater occurred during ebb and low tide. In 1990 and 1991 the salinity regime was polihaline, while in 1986 to 1987 it had a strong limnetic influence; and according to Cavalcanti et at' it was polihaline to limnetic before port implantation. Salinity fluctuations reflected a complex set of factors, namely the circulation in the estuary with the continuous discharge of the River Ipojuca partialy darned at its mouth. It is worth mentioning the change of the surface sediment distribution in the estuary that had high influence in the depth decrease and higher evaporation. Before the port implantation the sediment distribution in the estuary was predominantly determined by river action. The circulation was controlled by tidal movements and only a small contribution to estuarine sedimentation was made by marine sediments. After the reef partial opening the sediment was characterized by a fluvio-marine sand facies. Marine sediments that previously were transported to Suape Bay became traped at the estuary resulting in a sandfilling of the mouth area and the shifting of the main channel of the Ipojuca River (Neumann et a//). Surface and bottom dissolved oxygen saturation showed no clear trends, ranging from supersaturation to very low levels. Significant oxygen depletion was found during the ebb and low tide, mostly at dry season. The pH was always above 7.5. Water transparency was high during high tide for both seasons. Reduced levels were registered at the rainy season at low tide, due intense fine clay resuspension. A strong sedimentation near the river mouth decreased the local depth. This sedimentation summed up to the river- ocean partial closure transformed the estuary into a lagoon (Neumann et al.^). Rates of nutrient suply (NO?, NO^ PC>4 and SidJ varied seasonally; rainfall brought pulses from terrestrial run-off. Nutrients levels indicated eutrophy. Chlorophyll a oscillated continuously with higher values at the 1% light depth. Low tide and rainy season showed higher values (maximum 7.86 Transactions on Ecology and the Environment vol 27 © 1999 WIT Press, www.witpress.com, ISSN 1743-3541 Ecosystems and Sustainable Development 51 mg.m^). Chlorophyll a had strong correlation with nitrate and was considered low to a mangrove estuarine area (average of 3.07 mg.m"^ to the rainy season and 2.11 mg.m"^ to the dry season). 4.2 Plankton community analysis Tables 1 and 2 present the phytoplankton biodiversity.