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Pesce, M, Critto A, Torresan S, Giubilato E, Santini M, Zirino A, Ouyang W, Marcomini A.  2018.  Modelling climate change impacts on nutrients and primary production in coastal waters. Science of the Total Environment. 628-629:919-937.   10.1016/j.scitotenv.2018.02.131   AbstractWebsite

There is high confidence that the anthropogenic increase of atmospheric greenhouse gases (GHGs) is causing modifications in the Earth's climate. Coastal waterbodies such as estuaries, bays and lagoons are among those most affected by the ongoing changes in climate. Being located at the land-sea interface, such waterbodies are subjected to the combined changes in the physical-chemical processes of atmosphere, upstream land and coastal waters. Particularly, climate change is expected to alter phytoplankton communities by changing their environmental drivers (especially climate-related), thus exacerbating the symptoms of eutrophication events, such as hypoxia, harmful algal blooms (HAB) and loss of habitat. A better understanding of the links between climate-related drivers and phytoplankton is therefore necessary for projecting climate change impacts on aquatic ecosystems. Here we present the case study of the Zero river basin in Italy, one of the main contributors of freshwater and nutrient to the salt-marsh Palude di Cona, a coastal waterbody belonging to the lagoon of Venice. To project the impacts of climate change on freshwater inputs, nutrient loadings and their effects on the phytoplankton community of the receiving waterbody, we formulated and applied an integrated modelling approach made of: climate simulations derived by coupling a General Circulation Model (GCM) and a Regional Climate Model (RCM) under alternative emission scenarios, the hydrological model Soil and Water Assessment Tool (SWAT) and the ecological model AQUATOX. Climate projections point out an increase of precipitations in the winter period and a decrease in the summer months, while temperature shows a significant increase over the whole year. Water discharge and nutrient loads simulated by SWAT show a tendency to increase (decrease) in the winter (summer) period. AQUATOX projects changes in the concentration of nutrients in the salt-marsh Palude di Cona, and variations in the biomass and species of the phytoplankton community. (C) 2018 Elsevier B.V. All rights reserved.

Coronado-Alvarez, L, Alvarez-Borrego S, Lara-Lara JR, Solana-Arellano E, Hernandez-Ayon JM, Zirino A.  2017.  Temporal variations of water pCO(2) and the air-water CO2 flux at a coastal location in the southern California Current System: diurnal to interannual scales. Ciencias Marinas. 43:137-156.   10.7773/cm.v43i3.2707   AbstractWebsite

The aim of this work was to identify processes that cause surface CO2 partial pressure (pCO(2W)) and air-water CO2 flux (FCO2) variations at a coastal location in the California Current System, from semidiurnal to interannual time scales. Such processes may include sea breeze, upwelling, El Nino/Southern Oscillation (ENSO) cycle, and "The Blob" (strong positive temperature anomalies in the NE Pacific). Sea surface temperature (SST, 2008-2014) and pCO(2W) (2008-2015) time series were generated with data collected from a MAPCO(2) buoy anchored at 100 m depth and 5 km from Punta Banda (31.6 degrees N, 116.6 degrees W), Baja California, Mexico. There were significant changes in SST, pCO(2W), and FCO2 that lasted periods that were as short as a few hours and as large as interannual time frames. Spectral analysis showed significant semidiurnal, diurnal, similar to 15-d, and similar to 28-d components of variation. Time series were divided into periods according to the Multivariate ENSO Index and the Blob event. Bayesian t tests show that both pCO(2W) and FCO2 had high credibility of being different between periods. During La Nina conditions (2010-2011), maximum pCO(2W) and FCO2 values were higher, and the minimum values were lower, than during "normal," El Nino, and Blob conditions. The pCO(2W) range during this La Nina event was from 131 to 864 mu atm, and the FCO2 range was from -6.9 to 40.4 mmol C.m(-2).d(-1). The FCO2 range during the Blob was from near equilibrium to similar to 2.5 mmol C.m(-2).d(-1). The extreme values for the FCO2 integral (+/- standard error), for all periods, were -57.0 +/- 0.01 mmol C.m(-2) for El Nino, and 257.0 +/- 0.03 mmol C.m(-2) for La Nina. The mean FCO2 value (+/- standard error) was 0.04 +/- 0.02 mol C.m(-2).yr(-1). The buoy location was found to be a very weak source of CO2 during the study period.

Zirino, A, Elwany H, Facca C, Maicu F, Neira C, Mendoza G.  2016.  Nitrogen to phosphorus ratio in the Venice (Italy) Lagoon (2001-2010) and its relation to macroalgae. Marine Chemistry. 180:33-41.   10.1016/j.marchem.2016.01.002   AbstractWebsite

Analysis of the annually-averaged 2001-2010 monthly nutrient data from 13 stations in the Venice Lagoon (Italy) shows that the concentrations of dissolved nitrogen (N) species, measured as total dissolved N (TDN), have increased over time while that of phosphorus (P) species, measured as total dissolved P (TDP) have decreased. During the study period, the TDN/TDP ratio in the lagoon rose from about 46:1 to 100:1 (by atoms), a level at which the growth of benthic macroalgae is favored over that of sea grasses. The increase of the TDN/TDP ratio appears to be caused by two factors: (1) a small, but increasing amount of N in river water entering the lagoon, and (2) low P input combined with adsorption and entrapment of orthophosphate on colloidal iron oxides and carbonates at the water-sediment interface. This second mechanism would explain the increase in the TDN/TDP ratio, principally in zones of low salinity, where hydrodynamic residence times are long enough to permit N enrichment and result in macroalgal growth preferentially in the central, landward, side of the lagoon. However, an examination of the algal coverage of the lagoon floor from 2002 to 2010, indicates that while macroalgal abundance may be influenced by the N/P ratio, the spatial and temporal distribution during this period cannot be explained solely by this one feature. Nonetheless, this work points to the importance of considering the contributions that sediments in shallow lagoons make to the over-all system productivity and ecology and may be applicable to other shallow environments. (C) 2016 Elsevier B.V. All rights reserved.

Neira, C, Levin LA, Mendoza G, Zirino A.  2014.  Alteration of benthic communities associated with copper contamination linked to boat moorings. Marine Ecology-an Evolutionary Perspective. 35:46-66.   10.1111/maec.12054   AbstractWebsite

Although copper (Cu) is an essential element for life, leaching from boat paint can cause excess environmental loading in enclosed marinas. The effects of copper contamination on benthic macrofaunal communities were examined in three San Diego Bay marinas (America's Cup, Harbor Island West and East) in Southern California, USA. The distribution of Cu concentration in sediments exhibited a clear spatial gradient, with hotspots created by the presence of boats, which in two marinas exceeded the effect range medium (ERM). Elevated sediment Cu was associated with differences in benthic assemblages, reduced species richness and enhanced dominance in America's Cup and Harbor Island West, whereas Harbor Island East did not appear to be affected. At sites without boats there were greater abundances of some amphipods such as the species Desdimelita sp., Harpinia sp., Aoroides sp., Corophium sp., Podocerus sp., bivalves such as Lyonsia californica, Musculista senhousia, Macoma sp., and polychaetes such as Diplocirrus sp. In contrast, at sites with boats, densities of Pseudopolydora paucibranchiata, Polydora nuchalis, Euchone limnicola, Exogone lourei, Tubificoides spp. were enhanced. The limited impact on Harbor Island East suggests not only lower Cu input rates and increased water flushing and mixing, but also the presence of adequate defense mechanisms that regulate availability and mitigate toxic impacts. At all three marinas, Cu in tissues of several macrobenthic species exhibited Cu bioaccumulation above levels found in the surrounding environment. The annelids Lumbrineris sp. and Tubificoides spp., and the amphipod Desdimelita sp. contained high levels of Cu, suggesting they function as Cu bioaccumulators. The spionid polychaetes Polydora nuchalis and Pseudopolydora paucibranchiata had much lower Cu concentrations than surrounding sediments, suggesting they function as Cu bioregulators. The macrobenthic invertebrates in San Diego Bay marinas that tolerate Cu pollution (e.g. P.nuchalis, P.paucibranchiata, Euchone limnicola, Typosyllis sp., Tubificoides sp.) may function as indicators of high-Cu conditions, whereas the presence of Cu-sensitive species (e.g. Podocerus sp., Aoroides sp., Harpinia sp., Macoma sp., Lyonsia californica) may indicate healthier conditions (less Cu-stressed). Parallel responses by faunas of Shelter Island Yacht Basin, also in San Diego Bay, suggest potential for development of regional Cu contamination assessment criteria, and call for functional comparisons with other marinas and coastal water bodies.

Zirino, A, Elwany H, Neira C, Maicu F, Mendoza G.  2014.  Salinity and its variability in the Lagoon of Venice, 2000-2009. Advances in Oceanography and Limnology. 5(1):41-59.
Neira, C, King I, Mendoza G, Sellanes J, De Ley P, Levin LA.  2013.  Nematode community structure along a central Chile margin transect influenced by the oxygen minimum zone. Deep Sea Research Part I: Oceanographic Research Papers. 78:1-15.   AbstractWebsite

Nematodes are among the metazoans most tolerant of low-oxygen conditions and play major roles in seafloor ecosystem processes. Nematode communities were studied in sediments off Concepción, Central Chile, spanning the outer shelf within the OMZ (122 m) to the mid-lower continental slope (972 m) beneath the OMZ. The total density and biomass of nematodes (core depth 0–10 cm) ranged from 677 to 2006 ind. 10 cm−2, and 168.4 to 506.5 µg DW 10 cm−2, respectively. Among metazoan meiofaunal taxa, nematodes predominated at all sites both in terms of relative abundance (83.7–99.4%) and biomass (53.8–88.1%), followed by copepods, nauplii and polychaetes. Nematodes were represented by 33 genera distributed among 17 families, with densities greatest at low oxygen sites (122–364 m; ~2000 ind. 10 cm−2). Nematode generic and trophic diversity, and individual biomass were lowest, and Rank 1 dominance was highest, at the most oxygen-depleted site (122 m), despite the fact that the organic carbon content of the sediment was maximal at this depth. At the most oxygenated slope sites (827 and 972 m), all of Wieser's nematode feeding groups were represented. In contrast, at the lowest-oxygen site, only selective deposit (bacterial) feeders (1A) were present, indicating a reduction in trophic complexity. A large percentage of nematodes inhabited subsurface sediment layers (>1 cm). At deeper, more oxygenated sites (827 and 972 m), nematode individual biomass increased downcore, while within the OMZ, nematode biomass was low and remained relatively uniform through the sediment column. The concentration of nematodes in deeper sediment layers, the vertical distribution of the feeding groups, as well as the high nutritional quality of the deeper layers, suggest a differential resource partitioning of the food available, which may reduce interspecific competition.

Zirino, A, Neira C, Maicu F, Levin LA.  2013.  Comments on and implications of a steady-state in coastal marine ecosystems. Chemistry & Ecology. 29:86-99.   10.1080/02757540.2012.696613   AbstractWebsite

Coastal ecosystems can be thought of as being established by a number of physico-geochemical drivers, e.g. geochemistry and bathymetry of the basins, climate, tidal and freshwater flows, natural and anthropogenic inputs of nutrients and toxins, all of which exert an influence on the resulting communities of organisms. Depending on the interactions among the major drivers, ecosystems may occur on both large and small scales and be basin-wide or within basins. For individual and separate ecosystems to exist with some permanence in time, e.g. reach a steady-state, they also have to be ‘defended’. Defences are mechanisms that counter changes to maintain the status quo. We argue, and present evidence to support the notion, that the defence mechanisms are inextricably tied to primary production and the biogeochemical cycling of organic matter and provide buffers that mitigate potentially adverse impacts by trace toxins. Colloid pumping, production of complexing ligands and sulfide formation are some of the mechanisms that control trace substances. Current methods for assessing ecosystems do not address the issue of steady-state, nor do they take account of defence activities, e.g. buffering. Therefore, they cannot assess the ‘robustness’ of ecosystems or their ability to resist change, for good or bad. Also, defence mechanisms may, for a time, mask future potentially serious impacts, suggesting that monitoring efforts with limited budgets should consider the measurement of the inputs into ecosystems as well as the immediate or short-term result of the inputs. [ABSTRACT FROM PUBLISHER]Copyright of Chemistry & Ecology is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Neira, C, Mendoza G, Levin LA, Zirino A, Delgadillo-Hinojosa F, Porrachia M, Deheyn DD.  2011.  Macrobenthic community response to copper in Shelter Island Yacht Basin, San Diego Bay, California. Marine Pollution Bulletin. 62:701-717.   10.1016/j.marpolbul.2011.01.027   AbstractWebsite

We examined Cu contamination effects on macrobenthic communities and Cu concentration in invertebrates within Shelter Island Yacht Basin, San Diego Bay, California. Results indicate that at some sites, Cu in sediment has exceeded a threshold for "self defense" mechanisms and highlight the potential negative impacts on benthic faunal communities where Cu accumulates and persists in sediments. At sites with elevated Cu levels in sediment, macrobenthic communities were not only less diverse but also their total biomass and body size (individual biomass) were reduced compared to sites with lower Cu. Cu concentration in tissue varied between species and within the same species, reflecting differing abilities to "regulate" their body load. The spatial complexity of Cu effects in a small marina such as SIYB emphasizes that sediment-quality criteria based solely on laboratory experiments should be used with caution, as they do not necessarily reflect the condition at the community and ecosystem levels. (C) 2011 Elsevier Ltd. All rights reserved.

Neira, C, Delgadillo-Hinojosa F, Zirino A, Mendoza G, Levin LA, Porrachia M, Deheyn DD.  2009.  Spatial distribution of copper in relation to recreational boating in a California shallow-water basin. Chemistry and Ecology. 25:417-433.   10.1080/02757540903334197   AbstractWebsite

The overall effect of the number of boats on the copper (Cu) levels in the water column and sediment, along with their spatial variability within Shelter Island Yacht Basin (SIYB), San Diego Bay, California was examined. We identified a horizontal gradient of increasing dissolved Cu and Cu in sediment from outside to the head of SIYB which was coincident with the increasing number of boats. Spatial models of Cu distribution in water and sediment indicated the presence of 'hotspots' of Cu concentration. From outside to the head of SIYB, dissolved Cu ranged from 1.3 gL-1 to 14.6 gL-1 in surface water, and 2.0 gL-1 to 10.2 gL-1 in bottom water. Cu in sediment exceeded the Effect Range Low of 34mgkg-1 (i.e. where adverse effects to fauna may occur), with a peak concentration of 442mgkg-1 at the head of the basin. Free Cu++ in surface water was several orders of magnitude higher than in sediment porewater. High-resolution data of Cu species together with probability maps presented in this paper will allow managers to easily visualise and localise areas of impaired quality and to prioritise which areas should be targeted to improve Cu-related conditions.

Delgadillo-Hinojosa, F, Zirino A, Nasci C.  2008.  Copper complexation capacity in surface waters of the Venice Lagoon. Marine Environmental Research. 66:404-411.   10.1016/j.marenvres.2008.06.003   AbstractWebsite

Total copper (CUT), copper ion activity (pCu) and the copper complexation capacity (CuCC) were determined in samples of seawater collected in July 2003 from the Venice Lagoon. CUT and CUCC showed considerable spatial variability: Cu-T ranged from 1.8 to 70.0 nM, whereas the CuCC varied from 195 to 573 nM. pCu values varied from 11.6 to 12.6 and are consistent with those previously reported in estuarine and coastal areas (10.9-14.1).The range of CUT values compares well with those reported in the past in the lagoon and in the adjacent Adriatic Sea. The highest concentrations of CUT were found in samples collected near the industrial area of Porto Marghera, whereas the lowest were measured near the Chioggia and Malamocco inlets, where an intense tidally-driven renewal of seawater takes place. Although CuCC showed a high degree of spatial variability, the values recorded in the Venice Lagoon are comparable to those reported in other estuarine systems. In addition, CuCC was positively correlated with dissolved organic carbon (DOC), suggesting that organic ligands responsible for Cu complexation are part of the bulk organic matter pool in the lagoon. The CUCC:CUT molar ratio was, on average 55: 1, indicating that a large excess of complexation capacity exists in the Venice Lagoon. The high levels of CuCC and the narrow range of pCu indicates the importance of the role played by organic ligands in controlling the free ion Cu concentrations in the lagoon, and as a consequence, regulating its availability and/or toxicity. (C) 2008 Elsevier Ltd. All rights reserved.

Delgadillo-Hinojosa, F, Zirino A, Holm-Hansen O, Hernandez-Ayon JM, Boyd TJ, Chadwick B, Rivera-Duarte I.  2008.  Dissolved nutrient balance and net ecosystem metabolism in a Mediterranean-climate coastal lagoon: San Diego Bay. Estuarine Coastal and Shelf Science. 76:594-607.   10.1016/j.ecss.2007.07.032   AbstractWebsite

The temporal and spatial variability of dissolved inorganic phosphate (DIP), nitrogen (DIN), carbon (DIC) and dissolved organic carbon (DOC) were studied in order to determine the net ecosystem metabolism (NEM) of San Diego Bay (SDB), a Mediterranean-climate lagoon. A series of four sampling campaigns were carried out during the rainy (January 2000) and the dry (August 2000 and May and September 2001) seasons. During the dry season, temperature, salinity and DIP, DIC and DOC concentrations increased from oceanic values in the outer bay to higher values at the innermost end of the bay. DIP, DIC and DOC concentrations showed a clear offset from conservative mixing implying production of these dissolved materials inside the bay. During the rainy season, DIP and DOC increased to the head, whereas salinity decreased toward the mouth due to land runoff and river discharges. The distributions of DIP and DOC also showed a deviation from conservative mixing in this season, implying a net addition of these dissolved materials during estuarine mixing within the bay. Mass balance calculations showed that SDB consistently exported DIP (2.8-9.8 x 10(3) mol P d(-1)), DIC (263-352 x 10(3) mol C d(-1)) and DOC (198-1233 x 10(3) mol C d(-1)), whereas DIN (5.5-18.2 x 10(3) mol N d(-1)) was exported in all samplings except in May 2001 when it was imported (8.6 x 10(3) mol N d(-1)). The DIP, DIC and DOC export rates along with the strong relationship between DIP, DIC or DOC and salinity suggest that intense tidal mixing plays an important role in controlling their distributions and that SDB is a source of nutrients and DOC to the Southern California Bight. Furthermore, NEM ranged from -8.1 +/- 1.8 mmol C m(-2) d(-1) in September to -13.5 +/- 5.8 trunol C m(-2) d(-1) in January, highlighting the heterotrophic character of SDB. In order to explain the net heterotrophy of this system, we postulate that phytoplankton-derived particulate organic matter, stimulated by upwelling processes in the adjacent coastal waters, is transported into the bay, retained and then remineralized within the system. Our results were compared with those reported for the heterotrophic hypersaline coastal lagoons located in the semi-arid coast of Califomia-Baja California, and with those autotrophic hypersaline systems found in the semi-arid areas of Australia. We point out that the balance between autotrophy and heterotrophy in inverse estuaries is dependent on net external inputs of either inorganic nutrients or organic matter as it has been indicated for positive estuaries. (C) 2007 Elsevier Ltd. All rights reserved.

Hernandez-Ayon, JM, Zirino A, Dickson AG, Camiro-Vargas T, Valenzuela-Espinoza E.  2007.  Estimating the contribution of organic bases from microalgae to the titration alkalinity in coastal seawaters. Limnology and Oceanography-Methods. 5:225-232. AbstractWebsite

This study reports the potential contribution of organic bases to the alkalinity of seawater samples. The concentration of organic bases in these samples was inferred from the difference between the measured alkalinity and that calculated from a knowledge of pH and concentrations of the various inorganic acid- bases species such as total carbon, total boron, and so on. Significant concentrations of such organic bases were measured in cultures of the marine microalgae Rhodomonas sp. ( 800 mu mol kg (-1)) and Isochrysis aff. Galbana ( 400 mu mol kg (-1)), as well as in three marine environments ( northern gulf of California, mexico; San Quintin Bay, B. C., Mexico; and San Diego Bay). These three sites are characterized by significant biological activity and restricted mixing, and the organic bases were found at concentrations greater than 50 mu mol kg(-1) in each of these three locations.

Ignacio, RD, Rosen G, Lapota D, Chadwick DB, Kear-Padilla L, Zirino A.  2005.  Copper toxicity to larval stages of three marine invertebrates and copper complexation capacity in San Diego Bay, California. Environmental Science & Technology. 39:1542-1546.   10.1021/es040545j   AbstractWebsite

Temporal and spatial measurements of the toxicity (EC50), chemical speciation, and complexation capacity (Cu-CC) of copper in waters from San Diego Bay suggest control of the Cu-CC over copper bioavailability. While spatial distributions of total copper (CUT) indicate an increase in concentration from the mouth toward the head of San Diego Bay, the distribution of aqueous free copper ion (Cu(II)aq) shows the opposite trend. This suggests that the bioavailability of copper to organisms decreases toward the head of the bay, and is corroborated by the increase in the amount of copper needed to reach an EC50, observed for larval stages of three marine invertebrates (Mediterranean mussel, Mytilus galloprovincialis, sand dollar, Dendraster excentricus, and purple sea urchin, Strongylocentrotus purpuratus), and by the increase in Cu-CC heading into the head of the bay. The amount of Cu(II)aq required to produce a 50% reduction in normal larval development (referred to here as pCU(Tox)) of the mussel, the most sensitive of the three marine invertebrates, was generally at or above similar to 1 x 10(-11) mol L-1 equivalents of Cu (i.e., pCU(Tox) approximate to 11 = -(log [CU(II)aq])). These results suggest that the copper complexation capacity in San Diego Bay controls copper toxicity by keeping the concentration Of Cu(II)aq at nontoxic levels.

Boyd, TJ, Wolgast DM, Rivera-Duarte I, Holm-Hansen O, Hewes CD, Zirino A, Chadwick DB.  2005.  Effects of dissolved and complexed copper on heterotrophic bacterial production in San Diego Bay. Microbial Ecology. 49:353-366.   10.1007/s00248-003-1065-0   AbstractWebsite

Bacterial abundance and production, free (uncomplexed) copper ion concentration, total dissolved copper concentration, dissolved organic carbon (DOC), total suspended solids (TSS), and chlorophyll a were measured over the course of 1 year in a series of 27 sample "Boxes" established within San Diego Bay. Water was collected through a trace metal-clean system so that each Box's sample was a composite of all the surface water in that Box. Bacterial production, chlorophyll a, TSS, DOC, and dissolved copper all generally increased from Box 1 at the mouth of the Bay to Box 27 in the South or back Bay. Free copper ion concentration generally decreased from Box 1 to Box 27 presumably due to increasing complexation capacity within natural waters. Based on correlations between TSS, chlorophyll a, bacterial production or DOC and the ratio of dissolved to free Cu ion, both DOC and particulate (bacteria and algae) fractions were potentially responsible for copper complexation, each at different times of the year. CuCl2 was added to bacterial production assays from 0 to 10 mu g L-1 to assess acute copper toxicity to the natural microbial assemblage. Interestingly, copper toxicity appeared to increase with decreases in free copper from the mouth of the Bay to the back Bay. This contrasts the free-ion activity model in which higher complexation capacity should afford greater copper protection. When cell-specific growth rates were calculated, faster growing bacteria (i.e. toward the back Bay) appeared to be more susceptible to free copper toxicity. The protecting effect of natural dissolved organic material (DOM) concentrated by tangential flow ultrafiltration (> 1 kDa), illite and kaolinite minerals, and glutathione (a metal chelator excreted by algae under copper stress) was assessed in bacterial production assays. Only DOM concentrate offered any significant protection to bacterial production under increased copper concentrations. Although the potential copper protecting agents were allowed to interact with added copper before natural bacteria were added to production assays, there may be a temporal dose-response relationship that accounts for higher toxicity in short production assays. Regardless, it appears that effective natural complexation of copper in the back portions of San Diego Bay limits exposure of native bacterial assemblages to free copper ion, resulting in higher bacterial production.

Blake, AC, Chadwick DB, Zirino A, Rivera-Duarte I.  2004.  Spatial and temporal variations in copper speciation in San Diego Bay. Estuaries. 27:437-447.   10.1007/bf02803536   AbstractWebsite

Copper in estuaries has been an issue of concern for its toxicity to marine organisms. The ability to understand the processes that control copper speciation is a key factor towards achieving an improved assessment of the ecological risk it poses in the marine environment. Field measurements were made in August 2000, January 2001, May 2001, and September 2001 to provide a comprehensive view of circulation and water quality both spatially and temporally for the entire San Diego Bay. Rapid, underway, analysis of copper provided a unique, high-resolution view of total and labile copper species. The data show that total copper concentrations in San Diego Bay have been close to or above water quality criteria, increasing gradually from the lowest values in the mouth region (8 nM) to the innermost region (approximately 55 nM) with elevated concentrations existing in the Shelter Island and Commercial Basins. This work indicates that free copper activity ties between 10(-11) and 10(-13), and declines from the entrance to the head of San Diego Bay, even though the total copper concentration increases, a likely result of complexation with organic and particulate matter. Free copper measurements also show a seasonal dependence with the highest concentrations occurring 2 wk after a winter rain event in January 2001, reaching close to or above toxic levels in some locations.

Navarro-Olache, LF, Lavin MF, Alvarez-Sanchez LG, Zirino A.  2004.  Internal structure of SST features in the central Gulf of California. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 51:673-687.   10.1016/j.dsr2.2004.05.014   AbstractWebsite

Closely spaced XBT and CTD data were used to study the sub-surface structure of features observed in satellite AVHRR sea-surface temperature (SST) images of the Gulf of California (GC), such as fronts, jets and gyres. The lowest SSTs in the GC are found around the midriff islands, and especially over the sills, because of strong mixing from tidal currents and breaking internal waves. This minimum SST area is limited to the south and north by sharp SST fronts, which frequently show convolutions, gyres, and filaments. A vertical section of temperature along the Gulf length shows that about 300 km south of the sills, the isotherms begin to spread out in the vertical, reducing stratification. The thermocline isotherms begin surfacing about 100 km south of the sill, forming the SST minimum area, which has a maximum temperature difference of similar to6 degreesC with waters to the south and a horizontal SST gradient of similar to0.05 degreesC km(-1). The evolution and subsurface structure of a cool filament, apparently originated as an instability of the SST front, was intensely sampled. Satellite images show that its head advanced due south at about 0.5 ms(-1), along the edge of a pool of warm surface water about 110 km in diameter. The thermocline below the warm pool was raised at its edge, and some isotherms reached the surface, producing the cool filament. The tilt of the temperature, salinity and density isolines at the edge of the warm pool produced a geostrophic jet, adjacent to the cool filament and just inside the warm pool, with maximum speed similar to0.5 ms(-1) and extending down to similar to80 m. The filament lasted about 10 days, its width was similar to30 km and it reached a maximum length of similar to120 km. The volume transport of the jet in the top 100 m was around 0.7 Sv. (C) 2004 Elsevier Ltd. All rights reserved.

Hernandez-Ayon, JM, Zirino A, Marinone SG, Canino-Herrera R, Galindo-Bect MS.  2003.  pH-density relationships in seawater. Ciencias Marinas. 29:497-508. AbstractWebsite

In surface waters from the Southern Ocean and from the west coast of Baja California, a relationship was found between pH and water column density. In the Southern Ocean, pH was found to correlate well with density and salinity but not with temperature because water column stability was due to salinity. The opposite was found on the west coast of Baja California, where density was controlled by temperature. This demonstrates that pH follows density independently of what controls it. According to the results of this work, we suggest that pH-density correlations may be an important option in the development of algorithms for monitoring CO2 from satellite imagery.

Hernandez-Ayon, JM, Belli SL, Zirino A.  1999.  pH, alkalinity and total CO2 in coastal seawater by potentiometric titration with a difference derivative readout. Analytica Chimica Acta. 394:101-108.   10.1016/s0003-2670(99)00207-x   AbstractWebsite

A method for measuring three components of the CO2 system, pH, alkalinity (A(t)) and total CO2 (TCO2) in coastal seawater is presented. The measurements are sufficiently precise to register CO2 changes of biological origin in surficial and coastal waters or in culture media. The method is based on a modified potentiometric titration of seawater with acid in a custom-built cell with the data plotted as a difference derivative, giving two peaks from which total carbonate and alkalinity can be computed. pH is calculated directly from the initial millivolt reading of the sample. One important aspect of this technique is that, unlike a Gran titration, the measured values of pH, A(t) and TCO2 are independent of any pre-conceived seawater model. In this work we demonstrate that the relative position of the two peaks (used for determining TCO2) is relatively insensitive to interferences from dissolved organic matter to about 1 x 10(-4) M, while peak height is sensitive to it. This last observation permits the detection of organic bases which might be included in the measurement of alkalinity. (C) 1999 Elsevier Science B.V. All rights reserved.

Zirino, A, Belli SL, Van der Weele DA.  1998.  Copper concentration and Cu-II activity in San Diego Bay. Electroanalysis. 10:423-427.   10.1002/(sici)1521-4109(199805)10:6<423::aid-elan423>;2-v   AbstractWebsite

Copper ion activity and concentrations of voltammetrically defined dissolved, surface bound, and tightly bound colloidal copper in samples from San Diego Bay were measured independently using potentiometric and stripping voltammetric methods, respectively. 'Free' copper, calculated from activity, was approximately three orders of magnitude less than the concentrations of the dissolved, surface bound and tightly bound copper fractions (indicating a high degree of complexation) and over-all, was well correlated to them, suggesting a common, heterogeneous, copper matrix, of probable organic nature, whose distribution is controlled by physical mixing. This finding supports the aggregate or 'onion' model of copper speciation in seawater. Within the bay, we also encountered environments in which copper activity was not directly correlated to concentration and we attribute this to local production of organic ligands by microalgae.

Zirino, A, Fiedler PC, Keir RS.  1988.  Surface Ph, Satellite Imagery and Vertical Models in the Tropical Ocean. Science of the Total Environment. 75:285-300.   10.1016/0048-9697(88)90041-1   AbstractWebsite