Phytoplanktonic temporal variability in a coastal area of northwestern Baja California

A phytoplankton study was barried out in Bahía de Todos Santos from March 1986 to March 1987. Samples were taken monthly at three stations and at depths of 1, 10 and 20 m. The temporal variability of the phytoplankton taxonomic groups was very similar most of the time, except in June and November when an increase in the diatom group was detected. These cell blooms may be due to mixing processes or upwelling events that occur outside the study area. The advection process into the bay is shown by the low oxygen saturation values for June at 20 m depth. The size fractions of diatoms showed two successional phases of bloom events: in June, an abundance of cells was observed with late-bloom characteristics since the predominant cell size of the diatom group was > 20um, whereas in November there was a dominance of cells < 20 µm, characteristic of a prebloom event

Seasonal abundances of the harbor seal (Phoca vitulina richardsi Gray 1864), at Punta Banda Estuary (B.C., Mexico)

In order to know the present abundance and seasonal variability of the seals (Phoca vitulina richardsi Gray, 1864) hauling at the inner northwest portion of Punta Banda Estuary (Baja California, Mexico), 40 counts were carried out between November 1988 and August 1990. The average abundance during the study period was 52 individuals, although a significant seasonal variability was noted. The largest mean abundance occurred in spring (X = 69; n = 12; range = 31-110) and it was the best season to assess the number of seals that use the estuary. The lowest abundance was recorded in summer (X = 28; n = 5; range = 2-72) while in autumn the number of seals was lower than in winter and spring (X = 31; n = 8; range = 18-48). The maximum seal counts were noted in winter, although their average abundance was lower than in spring (X = 58; n = 15; range = 18-151) since the herd increased by the occasional presence of pups and juveniles. No relationship was found between the abundance of seals and the sea level. The seasonal variation in the size of the herd was associated with its breeding season which occurs late in winter and with herd movements to other near haul-out sites

The Estero de Punta Banda, B.C., Mexico as a link in the "Pacific Flyway": Abundance of shorebirds

Thirteen shorebird species and 5683 individuals were recorded at Estero Punta Banda from October 1988 to April 1989 in three soft-bottom habitats bordering the northern tip of the sand bar (open beach; terminal beach; mud-flats) and a semi-protected seasonal pond at the southwest comer of the estuary. The open beach (seven species; 1310 individuals), mud-flats (13 species; 3958 individuals) and the pond (two species; 146 individuals) harbored distinctive species assemblages while the terminal beach (five species; 239 individuals) acted as an extension of the open beach and mud flats. Most species where exclusive of a single habitat, or almost exclusive (species that occur in more that one habitat but exhibit strong quantitative differences among them). Seasonal changes were rather neat, although the study period missed the first part of the autumn migration towards the south. Seasonal movements were not synchronic in the different habitats. We estimated that about 14,000 shorebirds visit the lagoon each season (3,000 in the open beach; 11,000 in mud-flats). Although most species had been recorded for the site, quantitative data and evidence of the role of estero Punta Banda along the Pacific Flyway are offered in this study for the first time. Distinctive species assemblages in the different habitats, and asynchronism of migration in each, show that patchiness of habitats is important for the maintenance of species richness and for the conservation of the migratory process as well