Lack of a comprehensive knowledge of zooplankton of the coastal waters of the northeast region of Brazil prompted the present study. Seasonal and diurnal collections were made from an oil producing platform located off Ouamari, Rio Grande do Norte, %azi! during the period of one year from March 1987 to February 1988. A pneliminary analysis of the samples showed a discernible seasonal fluctu* atioD and a clear pattern of diurnal changes in the composition of zooplankton

Medeiros, G F

Rego, F A

Sankarankutty, C

Santos, N Q

Silva, I J

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NOTES ON ZOOPtANKTON OF THE COASTAL WATERS OP RIO GRANDE DO NORTE SAMPLED PROM OIL PRODUCING PLATFORM ABSTRACT Lack of a comprehensive knowledge of zooplankton of the coastal waters of the northeast region of Brazil prompted the present study. Seasonal and diurnal collections were made from an oil producing platform located off Ouamari, Rio Grande do Norte, %azi! during the period of one year from March 1987 to February 1988. A pneliminary analysis of the samples showed a discernible seasonal fluctu* atioD and a clear pattern of diurnal changes in the composition of zooplankton. THE COASTAL WATERS of the northeast region of Brazil have not been subjected to any detail-ed oceanographic study. Our present know-ledge on zooplankton of the Brazilian coastal waters is based on the studies of Vannucci and Hosoe (1952), Bjornberg and Forneris (1955, 1956 a, 1956 b), Hosoe (1956), Forneris (195?), Vannucci (1957), Almeida Prado (1961), Bjorn-berg (1963), Paranagua (1966) and Mcdeiros and Bjornberg (1978). The logistic support offered by the Brazilian Oil Company (Petrobras) to conduct observa-tions once a month on one of the offshore platforms gave the necessary impetus to carry out the present study. The financial support from the National Ootmcill for the Develop-ment of Science and Technology (ONPq) also contributed to the success of the project. The authors arc very much indebted to these organizations. Material and Methods The platform chosen (Fig. 1, PUB 3) is located about 26 kms from the coastal village of Guamare in the Siate of Rio Grande do Norte, Brazil. This platform offers a stable place on top of the emergency ladder placed on the shoreward side of this platform which remains appfoxiniately ten metres above water level and from which all samplings were done. The depth of water column varied from 12 to 14 metres. Sampling was done at an interval of four weeks and on the day of sampling, collections were made at about 1000 hrs and 2200 hrs. Collecting gears used were a Van Dorn water sampler for samples to determine physico-chemical parameters and a zooplankton net measuring 44 cm in diameter and a mesh size of 125/i. Water samples for analysis of physico-chemical parameters were taken at two depths (5 m and 10 m). Until the fabrication of a Van Dorn sampler only subsurface samples of water were collected and analysed. Physico-chemical parameters were studied only once a day (at 1000 hrs) except dissolved oxygen which was studied at 1000 hrs and at 2200 hrs on the day of sampling, Zooplankton samples were collected at 1000 hrs and at 2200 hrs and at every sampling three vertical hauls were made. To find out the vertical distrioution of zooplankton three depth profiles were sampled; frtm March to September - 10 mto surface and 5mio surface ; in October and November- 10 m to' surface NOTES 255 and bottom to surface ; from December to occurred in July and September, the latter February - only from bottom to surface. larger (1336/m») during the day. There was 7 , • , , , another drop in number towards the end of Zooplankton samples^ were analysed by September and again in October which was conventional method. Data expressed are as followed by another rise in number from organisms per cubic metre of water fihered. Average value from three samples for each depth profile was used in the estimation of density of population. November to February. Throughout the year all aight samples contained more organisms or rarely equal Fig. 1. The location of platform in the coastal waters of the State of Rio Grande do Norte, Brazil. Restiltx Among the physico-chemical parameters, temperature, transparency and dissolved oxygen showed moderate seasonal variations as can be seen in Table 1. There was only marginal fluctuation in salinity and pH values recorded. Zooplankton Seasonal fluctuation in the number of organisms was clearly evident during the study (Fig. 2 a). The number of organisms was low frcra March to June (lowest value 11/m» in April in the night). Two well defined peafo number (in May) of organisms except in September and February (Fig. 2 a). Attempts were made to elucidate the vertical distribution pattern by sampling different depth profiles. Extrapoliting these data, it was observed that the upper 5 metres of water column contained most of the organisms, irrespective of the time of sampling (Fig. 2 b). Copepoda Since Copepoda is the dominant component in the zooplanlcton, the pattern of seasonal fluctuation was tne same as that of zooplankton TABLE 1. Physico-chemical parameters 1987 1988 18th 14th 12th 9th 7th 4th 1st 29th 27th 24th 22nd 19th 23rd Wour Depth (m) Mar. Apr. May June July Aug. Sept. Sept. Oct. Nov. Dec. Jan. Feb-Transparency (m) 1000 6.0 6.0 6.0 12.0 8.0 10.0 9.5 10.0 11.0 3.0 4.0 5.5 5.5 Tanperature (°C) Hd 1000 Subsurf. 30.0 29.5 29.0 29.0 1000 5 10 1000 Subsurf. 1000 5 10 — 23.5 25.0 27.0 27.0 27.5 — 27.5 28.5 28.5 — 24.5 24.0 27.0 27.0 27.5 28.5 27.5 28.5 28.5 8.4 8.1 8.4 8.3 8.6 8.4 8.0 7.9 9.3 9.0 9.2 9.2 9.1 9.5 8.5 8.4 8.2 8.8 9.0 9.0 — O — a-8.3 ^ 8.4 Salinity (%„) 1000 Subsurf. 35.1 35.3 35.1 34.4 — 1000 5 10 35.0 34.9 38.0 37.0 36.5 36.0 36.0 35.4 37.4 35.0 34.9 38.0 37.0 37.0 36.0 36.5 35.0 37.1 Dissolved (O, ml/I) 1000 10 2200 5 10 4.59 5.06 4.80 3.80 3.78 3.08 4.34 4.10 4.82 3.62 3.98 2.72 5.70 5.70 4.50 5.40 4.44 4.48 4.48 5.07 5.80 3.80 ~ — 5.40 5.89 4.20 4.83 4.12 5.90 3.40 3.88 2.22 — 5.28 4.20 NOTES 257 12-| io. M 6 8 . C o 2. M t f c h - 0 ct . 1 0 m - 0 Oday • night 1 4tml J 1 12 10-" 6. 5*. March - Oct 10m-0 Dday • night **PwU M A M J J A S S O N D J F M A M J J A S S O N D J F M A Fig. 2 a. Seasonal and diurnal fluctuations of zooplankton sampled from two depth profiles, b. Vertical distribution of zooplankton during the day and night, c. Seasonal and diurnal fluctuations of Copepoda sampled from two depth profiles and d. Vertical distribution of Copepoda duiing the day and night. (Fig. 2 c). Lowest number of copepods occurred in April (,10/m') and largest number in early September (l22/ra*). As a whole, night samples contained more copepods compared to those taken during the day, except in May and early September when the reverse was true (Fig. 2 c). Fig. 2 d shows that most of the population of copepods remains in the upper 5 metre Wiater column irrespective of the time of sampling. 17 Appendicularla From Fig. S a it can be seen that three peaks occurred, first in April, second in the early part of September and third in December. Appendicularians, in general, were well repre-sented during the period July—jarly part of September and again from November to Februrary. They almost disappeared in the day samples of March to June and again in late September and November. . They were normally more abundant in the £58 NOTES Oct. - Feb. bottom - Om D day B n ight M A M J J A S S O N D J F 16-U 212 M 10. 8. 6-gs'^ -V-o n day a night M A M J J A S Fig. 3 a. Seasonal and diurnal fluctuations of Appendicularia sampled from two depth prolilcs and b. Vertical distribution of Appendicularia during the day and night. night samples (Fig, 3 a), except in early September and October when they appeared in large number during the day. It can be seen from Fig. 3 b that appendicula-rians were mostly contoed to the upper layer except in September when there were few organisms in the upper layer. Chaetognatha The nimtber of Chaetognatha was low except for a period between May and August when a distinct peak was observed in July (Fig. 4). Fig. 4, Seasonal and dituoal fluctuatioxt of Chaetognatha sampled from two depth profiles. Invariably night samples had more Chaeto gnatha. Discussion In tropical waters seasonal fluctuation is not considered a significant feature compared to colder waters. Though this holds true in the case of oceanic region, seasonal fluctuation is rather well pronounced in tropical and sub-tropicsl estuaries (Reeve, 1964; Esnal et al.-1985) and inshore waters (Wickstead.. 1958) where the nutrient salts play a decisive role in the seasonal fluctuation. The ecosystem studied which is situated in a tropical region within the continental shelf, does not present any profound seasonal changes in the physico-chemical parameters. As such, these parameters are not likely to influence much in the fluctuation in plankton rroductioD. The moderate fluctuation obser-ved during this study is within the limits of NOTES 259 tolerance of most of the tropical zooplankton. related to the fluctuation in tlie nutrient Therefore, the observed seasonal variation in content which has a direct influence on phyto-zooplankton number is likely to be indirectly plankton production. Departamento de Oceanograpia e Limnologia, Universidade Federal do Rio Grande no Norte, Natal RN-59000, Brazil C. SANKARANKUTTY G. F. MBDEIROS N. Q. SANTOS I. J. SiLVA F. A. REGO REFERENCES ALMEIDA PRAOO, M. H. 1961. Bol. Inst. Oceanogr. Sao Paulo, 11 (2) : 31-56. BjoRNBERO, T. K. S. 1963. Ibid., 8 (1): 1-142. AND L. FoRNERis 1955. Coittr. Avid. Inst. Oceanogr. Sao Paulo, 1 : 1-68. •AND-Sao Paulo, S (7)-.105.111. 1956 a. Bol. Inst. Oceanogr. AND 1956 b. Ml., 7 : 113-116. EsNAL, G. B., C. SANKARANKUTTY AND R . J. CASTRO 1985. Physis {Buenos Aires), Secc. A, 43 (105): 65-71. Fc«NERls, L. 1957. 273.284. An. Acad, Bras. Cien., 29 '• HosoE, K. 1956. Contr. Ayul. Inst. Oceanogr. Sao Paulo, 3:1-9. MEDEIROS, O , F . AND T . K . S. BJORNBERG 1978. Ciencia e Cultura, Sao Paulo, 30 (3) : 348-349. PARANAQUA, M . N . 1966. Trab. Inst. Oceanogr. Univ. Fed. Pe., Recife, 5/6 (1): 125-141. REEVE, M . R. 1964. Bull. Mar. Sci. GulfSt Carib,. 14:103-121. VANNUCCI, M . 1957. Bol. Inst. Oceanogr. Sao Paulo, 8 (1-2): 23-109. AND HOSOB 1952. Ibid., 5 (3): 1-30. WlCKSTBAD, J. H. 1958. / . Cons. int. Explor. Mer., 23:340-353. 

On zooplankton of the coastal waters of Rio Grande Do Norte sampled from oil producing platform

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On zooplankton of the coastal waters of Rio Grande Do Norte sampled from oil producing platform

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