Topographically, the Gulf of California is divided into a series of basins and trenches that deepen to the south. Maximum depth at the mouth is greater than 3000 m. Most of the northern gulf is less than 200 m deep. The gulf has hydrographic features conducive to high primary productivity. Upwelling events have been described on the basis of temperature distributions at the eastern coast during winter and spring and at the western coast during summer. Tidal amplitude may be as high as 9 m in the upper gulf. On the basis of discrete phytoplankton sampling, the gulf was previously divided into four geographic regions. This division took into consideration only the space distribution, taxonomic composition, and abundance of microphytoplankton. With the availability of the coastal zone color scanner (CZCS) imagery, we were able to include the time variability of pigments to make a more detailed biogeographic division of the gulf. With weekly composites of the imagery, we generated time series of pigment concentrations for 33 locations throughout the gulf and for the whole life span of the CZCS. The time series show a clear seasonal variation, with maxima in winter and spring and minima in summer. The effect of upwelling at the eastern coast is clearly evident, with high pigment concentrations. The effect of the summer upwelling off the Baja California coast is not evident in these time series. Time series from locations on the western side of the gulf also show maxima in winter and spring that are due to the eddy circulation that brings upwelled water from the eastern side. Principal-component analysis was applied to define 14 regions. Ballenas Channel, between Angel de la Guarda and Baja California, and the upper gulf always appeared as very distinct regions. Some of these 14 regions relate to the geographic distributions of important faunal groups, including the benthos, or their life cycles. For example, the upper gulf is a place for reproduction and the nursery of many fish species, marine mammals and birds are specially abundant in Ballenas Channel, sardine spawning mostly occurs in the central gulf in spring, and shrimp are abundant off mainland Mexico. 7411

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The 1982-1984 El Nifio was well documented for the Gulf of California, primarily with sea level anomalies. However, owing to strong tidal and atmospheric forcing, the general effects on chlorophyll concentrations ([Chl]) and phytoplankton productivity (PP) are not clear. The literature reports low [Chl] and PP for the mouth region and high values for both variables in the central gulf and in the region of the midrift islands. No data were collected in situ in the northern gulf. Using monthly composites of coastal zone color scanner (CZCS) satellite imagery, we generated time series for 33 locations throughout the gulf. We calculated pigment concentration anomalies and derived a relative power index that provides a measure of the relationship between negative anomalies and El Nifio episodes. Our analyses show that during 1978-1986, variability in phytoplankton biomass in the Gulf of California was not dominated by El Nifio events. Rather, strong tidal mixing and upwelling in the interior of the gulf masked the effect of El Nifio 1982-1984 that otherwise showed so clearly in other coastal ecosystems of the eastern Pacific. Lower pigment concentrations were in fact detected with the CZCS at and near the entrance of the gulf, where vertical mixing is not as strong. Locations in the central and northern gulf showed either a weak effect or no effect of El Nifio. Ballenas Channel showed an exceptional behavior, with an increase of pigment concentrations toward the end of 1983. Despite the Ballenas Channel having the highest surface nutrient concentrations, pigment maxima there are not in general the highest of the gulf. The excess vertical turbulence in the channel leads to light limitation of phytoplankton. Reduced mixing at the end of 1983 promoted the increase of phytoplankton biomass in Ballenas Channel. Strong non-El Nifio conditions in 1984 caused lower phytoplankton biomass in Ballenas Channel than during other years of the period analyzed. Introduction E1 Nifio-Southern Oscillation episodes severely reduce primary productivity throughout most of the coastal eastern Pacific, from Peru to Baja California and California [Barber and Chavez, 1983; Cane, 1983]. Some of the changes observed during an event are unusually high sea surface temperatures, poleward coastal currents, heavy rainfall, invasion by tropical organisms, and mass mortality of various local marine organisms. Wooster [1960] was the first to suggest that the anomalies in both Peru and California had the same underlying causes. McGowan [1983] indicated that primary and secondary production in the California Current are high when the transport of cool, low-salinity water from the north is strong and low when it is weak; the periods of warming and low production in the California Current tend to coincide with E1 Nifio events in the eastern equatorial Pacific. The strongest recorded E1 Nifio event began to develop in the equatorial Pacific during the summer of 1982 [Rasmusson, 1984]. Tidal records show the E1Nifio developing at the end of 1982 as positive ...

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Coastal lagoons are transitional ecosystems with complex spatial and temporal variability. Remote sensing tools are essential for monitoring and unveiling their variability. Turbidity is a water quality parameter used for studying eutrophication and sediment transport. The objective of this research is to analyze the monthly turbidity pattern in a shallow coastal lagoon along two years with different precipitation regimes. The selected study area is the Albufera de Valencia lagoon (Spain). For this purpose, we used Sentinel 2 images and in situ data from the monitoring program of the Environment General Subdivision of the regional government. We obtained Sentinel 2A and 2B images for years 2017 and 2018 and processed them with SNAP software. The results of the correlation analysis between satellite and in situ data, corroborate that the reflectance of band 5 (705 nm) is suitable for the analysis of turbidity patterns in shallow lagoons (average depth 1 m), such as the Albufera lagoon, even in eutrophic conditions. Turbidity patterns in the Albufera lagoon show a similar trend in wet and dry years, which is mainly linked to the irrigation practice of rice paddies. High turbidity periods are linked to higher water residence time and closed floodgates. However, precipitation and wind also play an important role in the spatial distribution of turbidity. During storm events, phytoplankton and sediments are discharged to the sea, if the floodgates remain open. Fortunately, the rice harvesting season, when the floodgates are open, coincides with the beginning of the rainy period. Nevertheless, this is a lucky coincidence. It is important to develop conscious management of floodgates, because having them closed during rain events can have several negative effects both for the lagoon and for the receiving coastal waters and ecosystem. Non-discharged solids may accumulate in the lagoon worsening the clogging problems, and the beaches next to the receiving coastal waters will not receive an important load of solids to nourish them.

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[1] Ocean color (OCTS, SeaWiFS) and sea surface temperature (AVHRR) images were used to evaluate spatial and temporal variability of the Brazil-Malvinas Confluence and La Plata Plume (20°to 45°S and 40°to 65°W). The data set covers the period from January 1997 to June 2003. Chlorophyll and SST data were combined using Principal Component Analysis (PCA). The results yielded were used to identify and follow front displacements. PCA maps showed a close relationship with previous observations of currents behavior and the La Plata Plume. Firstly the analysis was performed on data retrieved from a monthly climatology, and the results show three remarkable features: a gradual increase of the northward intrusion of the La Plata Plume throughout the period lasting from summer to winter; the summer shape of the La Plata Plume showed a stronger penetration over the shelf on the Argentinean side of the estuary mouth; and the seasonal migration of the Brazil-Malvinas Confluence. Monthly composites were then used and compared with discharge and wind data from scatterometers. The results show that increases on discharge led to a greater influence of the La Plata Plume over the continental shelf although during 1998 (El Niño) it did not penetrate farther north because of the unfavorable wind pattern (northerly). On the other side, during 2002, high discharge rates were associated with strong southerly winds, leading to a northern penetration of the plume. The same analysis was applied to daily images to show its application on locating the front's position. This analysis showed the same patterns.Citation: Gonzalez-Silvera, A., E. Santamaria-del-Angel, and R. Millán-Núñez (2006), Spatial and temporal variability of the BrazilMalvinas Confluence and the La Plata Plume as seen by SeaWiFS and AVHRR imagery,

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