From 1995 to 2000, daily integrated, water column phytoplankton primary production was estimated at the CaTS (Caribbean Time-Series Station, 17 deg 36’N, 67 deg 00’W) using available algorithms that relate phytoplankton photosynthetic pigment biomass and available photosynthetic radiation (PAR). Radiocarbon experiments using a photosynthetron were conducted to generate P vs. E (photosynthesis vs. irradiance) curves from which to obtain the photosynthetic parameters alpha, the Maximum Light Utilization Coefficient (from 0.01 to 0.19 ([mg C mg chla^-1 hr^-1] [microEinstein m^-2 sec^-1]^-1) and PBS, the Potential Maximum Photosynthetic Rate (from 0.56 to 3.49 mg C m^-3hr-^1). Average daily integrated primary production was between 132 and 750 mg C m^-2 d^-1. Annual production was 149 g C m^-2 yr^-1 and showed maxima in April, July, October and November. SeaWiFS derived chlorophyll-a concentrations for the Northeastern Caribbean Sea followed the same pattern. Increases in primary production were associated to large PBS (or PBM), alpha and â*ph values during maximum influence of Amazon and Orinoco River plume waters. A deeper euphotic layer was observed from February to April and in July reaching down to 166 m. Maximum solar irradiance at the end of April and a deep euphotic layer allow maximum light penetration that can easily reach the deep chlorophyll-a maximum located near 100 m. High vertical diffusivity values, kappa > 6 X 10^-3 m^-2 s^-1, were measured between SEP-DEC 1997 and MAY-OCT 2000 in oceanic waters of the Mona Passage. These elevated diffusivities are associated with the presence of locally generated internal waves of semidiurnal frequency (internal tide), with a reduction of the Richardson number at the base of the pycnocline, and with increased coastal seiches activity over the southwest coast of Puerto Rico. The patterns of activity are strictly correlated with the lunar cycle and with changes in the stratification of the Caribbean Surface Water (CSW). Increases in the stratification of the water column are due to the influence of the Amazon and Orinoco Rivers. Under the proper astronomical forcing and vertical stratification conditions energy from the barotropic tide at or near the shelf break is transferred offshore towards the generation of internal tides and shoreward into the platform waters consequently increasing the coastal seiche activity. Internal tides of near-semidiurnal frequencies were observed in the euphotic zone. The maximum observed height (crest to trough) was 26 m. Maximum concentrations of chlorophyll-a (1.2 mg Chl-a m^-3) occurred near the crest during high upward velocities (> 40 m h^-1). Additionally, increases in vertical eddy diffusivity above 6 x 10^-3 m^2 s^-1 were observed one hour before the arrival of the internal tide trough. The development of K-H instabilities during the breaking of the internal tide can explain the formation of high diffusivity patches. Inside the patches (kappa > 0.004 m^2 s^-1) increments in primary productivity of the order of 0.05 mg C m^-3 h^-1 were measured. The patches generated a NO3 flux equal to 1.058 x 10^-4 mmol m^-2 s^-1 and can sustain a new production equal to 724 mg C m^-2 d^-1 or 264 g C m^-2 yr^-1. These numbers are much higher than the estimates attributed to mesoscale eddies. Higher values of primary productivity were observed near the wave trough, than those observed during periods of maximum solar irradiance at noon. Significant changes in the attenuation coefficient (from 0.03 m^-1 to 0.05 m^-1) for the following SeaWiFS bands: 412, 443, 490 and 512 nm corresponded to events of maximum upward velocities and higher diffusivity. These processes seem to be easy to detect in oceanic waters, out of the influence from high nutrient load waters due to river discharge.