Studies on picophytoplankton in the southern Gulf of Mexico: recognition of picoprokaryotes and abundances of picophytoplankton during "dry season"

• Published in: Brazilian journal of oceanography 2013-12, Vol.61 (4), p.265-276
• Main Authors: Aquino-Cruz, Aldo, Hernández-Becerril, David Uriel, Signoret-Poillon, Martha, Salas-de-León, David Alberto, Monreal-Gómez, María Adela
• Format: Article
• Language: English
• Subjects: Abundância; Distribuição; MARINE & FRESHWATER BIOLOGY; OCEANOGRAPHY; Picofitoplâncton; Prochlorococcus; sul do Golfo do México; Synechococcus
• ISSN: 1679-8759; 1982-436X; 1679-8759
• DOI: 10.1590/S1679-87592013000400007

The abundance and distribution of total autotrophic picophytoplankton (PFP), temperature, salinity, PAR, and chlorophyll a were determined in two presumably contrasting environments: (1) two coastal areas (close to the mouths of three rivers), and (2) one oceanic area (Campeche Canyon), of the southern Gulf of Mexico, during the "dry season" (June-July, 2004). The picoprokaryotes Prochlorococcus and Synechococcus were identified by TEM, whereas Synechococcus and picoeukaryotes populations were also recognized by flow cytometry. The highest PFP abundance (1.67×105 cells ml-1) was found in shallow waters (~10 m depth) around the Grijalva-Usumacinta river mouth, followed by that found at a station close to the Coatzacoalcos River (1.19×105 cells ml-1); PFP abundances in the Campeche Canyon were usually lower (maximum 1.53×104 cells ml-1). Greater variability in PFP abundances was found in coastal stations than in oceanic waters, and weak relationships appeared between the patterns of chlorophyll a and PFP abundance. Peaks of PFP were detected in both coastal and more oceanic areas, but in the Campeche Canyon they were located deeper (60 m), relatively closer to the deep maximum of chlorophyll (located at about 75 m). Results suggest that PFP populations include a substantial photosynthetic component in both coastal and oceanic waters of the southern Gulf of Mexico. Abundância e distribuição do picofitoplâncton autotrófico total (PFP), temperatura, salinidade, PAR e clorofila-a, foram determinados em dois ambientes presumivelmente diferentes: (1) duas áreas costeiras (perto da foz de três rios) e (2) uma área oceânica (Campeche Canyon), ambas situadas ao sul do Golfo do México, durante a "estação seca" (Junho-Julho, 2004). Os picoprocariontes Prochlorococcus e Synechococcus foram identificados por TEM, e as populações de Synechococcus e de picoeucariontes também foram reconhecidas por citometria de fluxo. A maior abundância de PFP (1,67 × 105 células ml-1) foi encontrada em águas rasas (~ 10 m de profundidade) em torno dos rios Grijalva Usumacinta, seguida de uma estação perto do Rio Coatzacoalcos (1,19 × 105 células ml-1). As abundâncias de PFP em Campeche Canyon foram geralmente menores (máximo 1,53 × 104 células ml-1). A maior variabilidade em abundâncias de PFP foi encontrada em estações costeiras quando comparado às águas oceânicas, e quase não houve correlação entre os padrões de clorofila-a e abundância de PFP. Picos de PFP foram detectados nas áreas co