SUMMARY: The annual cycle of plankton was studied over 14 years from 1984 to 2000 at a coastal station in the Gulf of Naples, with the aim of assessing seasonal patterns and interannual trends. Phytoplankton biomass started increasing over the water column in February-early March, and generally achieved peak values in the upper layers in late spring. Another peak was often recorded in autumn. Diatoms and phytoflagellates dominated for the largest part of the year. Ciliates showed their main peaks in phase with phytoplankton and were mainly represented by small (< 30 µm) naked choreotrichs. Mesozooplankton increased in March-April, reaching maximum concentrations in summer. Copepods were always the most abundant group, followed by cladocerans in summer. At the interannual scale, a high variability and a decreasing trend were recorded over the sampling period for autotrophic biomass. Mesozooplankton biomass showed a less marked interannual variability. From 1995 onwards, phytoplankton populations increased in cell number but decreased in cell size, with intense blooms of small diatoms and undetermined coccoid species frequently observed in recent years. In spite of those interannual variations, the different phases of the annual cycle and the occurrence of several plankton species were remarkably regular.Key words: Mediterranean Sea, phytoplankton, ciliates, mesozooplankton, seasonal cycle, long term series. RESUMEN: PATRONES ESTACIONALES EN LAS COMUNIDADES PLANCTÓNICAS EN UNA SERIE TEMPORAL PLURIANUAL EN UNA LOCALIDAD COSTERA DEL MEDITERRÁNEO (GOLFO DE NÁPOLES): UN INTENTO DE DISCERNIR RECURRENCIAS Y TENDENCIAS.-El ciclo anual del plancton se estudió a lo largo de 14 años, desde 1984 a 2000, en una estación costera del golfo de Nápoles, con el objetivo de discernir pautas estacionales y tendencias interanuales. La biomasa fitoplanctónica empezaba a aumentar en la columna de agua en febrero-primeros de marzo, y generalmente alcanzaba valores máximos en las capas superiores a finales de primavera. Se solía registrar otro máximo en otoño. Las diatomeas y los fitoflagelados dominaron durante la mayor parte del año. Los ciliados presentaron sus máximos principales en fase con el fitoplancton y estuvieron representados principalmente por pequeños (< 30 µm) coreotricos desnudos. El mesozooplancton aumentó en marzo-abril, llegando a concentraciones máximas en verano. Los copépodos fueron siempre el grupo más abundante, seguidos de los cladóceros en verano. A la escala interanual, la biomasa autotrófica registró una elevada variabilidad y una tendencia decreciente a lo largo del período de muestreo. La biomasa del mesozooplancton mostró una variabilidad interanual menos marcada. Desde 1995 en adelante, las poblaciones de fitoplancton aumentaron en número de células, pero el tamaño celular se redujo, y en años recientes se han observado floraciones intensas de diatomeas pequeñas y de especies cocoides no determinadas. A pesar de estas variaciones interanuales, las distintas fases del ciclo anual y la presencia de varias es...

Seasonal variations in tintinnid abundance and species composition were studied weekly for 4 yr at a coastal site in the Gulf of Naples (Tyrrhenian Sea). Of the 57 identified tintinnid species, only 7 accounted for 81% of tintinnid abundance. Recurrent seasonal patterns were observed for the most common species. The characteristics of the tintinnid community over this 4 yr study are similar to those reported for tintinnid assemblages at the same study site in 1984-85 in terms of total abundance, species composition and timing of the dominant species. According to reports in the literature the persistence in time of the dominant tintinnid species appears to be a general feature, a sort of 'fingerprint' of each area. In contrast, in the Gulf of Naples only Tintinnopsis beroidea, reported as dominant in 1934, continues to be dominant in this area today; the other dominant species of the 1930s were rarely found during this study. Changes and persistence of tintinnid species in the Gulf of Naples are discussed in relation to major changes in phytoplankton populations in the period 1984 to 2000. Chlorophyll concentrations integrated over the whole water column are now only 50% of the former values and only 34% of former surface values. We also compare our findings to reports from other coastal sites to evaluate the distribution of key tintinnid species, in particular for the western Mediterranean Sea. KEY WORDS: Tintinnids · Diversity · MediterraneanResale or republication not permitted without written consent of the publisher

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