Pupping and molting of Phoca vitulina are processes that occur each year with high precision, although their timing varies according to location. Knowledge about the timing of these events allows us to determine when the highest numbers of individuals are hauled out, which is important to achieve a good abundance estimation. In this study we determined the timing of pupping and molting of P. v. richardii at Punta Banda Estuary, Baja California (Mexico), previously unknown at this site or along its entire distribution in Mexico. Observations were carried out during the 2011 and 2012 pupping seasons, as well as the 2012 molting season. We determined that the pupping season starts in mid-February and ends in mid-April, and that the maximum number of pups occurs in mid-March. The late premolt stage was observed from the end of March to the beginning of July, with the peak proportion of individuals in this stage at the beginning of May. The molting period extends from the end of April to mid-July, with the peak proportion of individuals molting at the beginning of June. The reverse molt pattern (starting on the torso and ending on the head and flippers) was the most common. The highest number of adult and subadult individuals on land was observed during the molting season; therefore, the best time to carry out counts to estimate seal abundance in this area is from the beginning of May to the beginning of June.

Assessments of picoplankton carbon biomass in the pelagic ecosystem over the deep region of the southern Gulf of Mexico were conducted during three consecutive summer cruises. Notably, the relationship between carbon distribution of Prochlorococcus (PRO) and Loop Current (LC) dynamics was evaluated. Seawater samples were collected from the euphotic zone (~150 m) for estimating the abundance of the picoplankton populations using flow cytometry analyses. Carbon biomass estimates were based on cell abundance and variable conversion factors computed across stations and depths. On average, about half of the total depth-integrated carbon biomass of picoplankton was attributed to heterotrophic bacteria (HB, 54%) and three autotrophic populations (Prochlorococcus, Synechococcus, and pico-eukaryotes, 46%). In agreement with previous winter assessments, PRO was the dominant component of abundance (~90%) and pico-phytoplankton community biomass (>70%). Based on molecular analyses, distinct ecotypes of high-light PRO and low-light (LL) PRO were found within the euphotic zone, vertically distributed along light and nutrient gradients. Also, PRO distributions were related to hydrographic conditions strongly modulated by mesoscale dynamics. LL-PRO subgroups, located close to the nutricline under LL conditions, were associated with the westward propagation of anticyclonic eddies that episodically detach from the LC. This study highlights the role of the LC and its eddies in the transport and distribution of carbon biomass into the Gulf of Mexico, as represented by the deep subgroups of the dominant, tiniest autotroph within this oligotrophic ecosystem.

We document and compare the annual molt of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the west coast of the Baja California Peninsula that are the northern and southern extremes of its distribution in Mexico. During 2014, observations were made from March to July on Todos Santos Island (northern extreme) and from January to June on San Roque Island (southern extreme). On Todos Santos, the premolt lasted 15 wk (March–June) and the molt 12 wk (April–July). On San Roque, the premolt lasted 22 wk (January–June) and the molt 17 wk (February–June). The proportion of seals undergoing molt peaked on 26 May on Todos Santos and on 7 June on San Roque. Shedding of old hair most commonly initiated on the torso and progressed to the head and flippers (reverse molting pattern). The period when the highest number of harbor seals haul out in Mexico is in late April on the more southerly islands and in early May on the more northerly islands, when a large proportion of seals are in premolt.

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