Todos Santos Bay Research Articles

The carbonate system in coastal waters off the northern region of the Baja California Peninsula under La Niña conditions

In the North Pacific, variations in isopycnal depth influence the biogeochemical characteristics of the water column and the aragonite saturation horizon (ZΩa) during interannual events. The objective of this study was to assess the effect of the 2011 La Niña conditions on ZΩa in Todos Santos Bay (Baja California, Mexico) and surrounding waters. The results showed that ZΩa variability was modulated by the intensity of interannual conditions and by the water masses that were present in the region. Subarctic Water predominated in the upper 200 m with anomalous characteristics, such as low temperature and low salinity. Also, isopycnals shoaled toward the coast and ZΩa was thus ~30 m in the nearshore area, in contrast with the oceanic region, where ZΩa was ~150 m. Prior to this study, there were no records of ZΩa in Todos Santos Bay, nor were there any records of its shallowness.

Physical and biogeochemical variability in Todos Santos Bay, northwestern Baja California, derived from a numerical NPZD model

A physical-biogeochemical Nitrate-Phytoplankton-Zooplankton-Detritus (NPZD) numerical model is used to study the variability of coastal phytoplankton biomass in northwestern Baja California and the Todos Santos Bay (TSB), a region of high socioeconomic importance located in the southern California Current System. The model reproduces adequately the most important oceanographic features of the study area, like the coastal chlorophyll-a (Chl-a) maxima and thermal gradients in the regions of enhanced coastal upwelling. The variability of Chl-a in the TSB is influenced by the activity of El Niño-Southern Oscillation (ENSO) and decadal modes of the Pacific, e.g., the Pacific Decadal Oscillation (PDO) and the North Pacific Gyre Oscillation (NPGO). From de multi-year model simulation (2004–2011), this large-scale influence is remarkable in two contrasting anomalous years. The year 2006 was anomalously warm and with low Chl-a levels, associated with warm phases of ENSO and PDO and a weakening of the NPGO. These climatic anomalies caused a strong stratification and weak upwelling around the TSB, which induced a poor nutrient input into the Bay and a deep and weak subsurface Chl-a maximum (SCM) during summer. The year 2011, on the other hand, was a cold year with enhanced upwelling during the spring, associated with cold phases of ENSO and PDO and an intensification of the NPGO. These conditions also caused a weak stratification and an intense nutrient transport into the TSB and hence a shallower and stronger SCM.

Identification of Phytoplankton Blooms under the Index of Inherent Optical Properties (IOP Index) in Optically Complex Waters

Phytoplankton blooms are sporadic events in time and are isolated in space. This complex phenomenon is produced by a variety of both natural and anthropogenic causes. Early detection of this phenomenon, as well as the classification of a water body under conditions of bloom or non-bloom, remains an unresolved problem. This research proposes the use of Inherent Optical Properties (IOPs) in optically complex waters to detect the bloom or non-bloom state of the phytoplankton community. An IOP index is calculated from the absorption coefficients of the colored dissolved organic matter (CDOM), the phytoplankton ( phy ) and the detritus (d), using the wavelength (λ) 443 nm. The effectiveness of this index is tested in five bloom events in different places and with different characteristics from Mexican seas: 1. Dzilam (Caribbean Sea, Atlantic Ocean), a diatom bloom (Rhizosolenia hebetata); 2. Holbox (Caribbean Sea, Atlantic Ocean), a mixed bloom of dinoflagellates (Scrippsiella sp.) and diatoms (Chaetoceros sp.); 3. Campeche Bay in the Gulf of Mexico (Atlantic Ocean), a bloom of dinoflagellates (Karenia brevis); 4. Upper Gulf of California (UGC) (Pacific Ocean), a diatom bloom (Coscinodiscus and Pseudo-nitzschia) and 5. Todos Santos Bay, Ensenada (Pacific Ocean), a dinoflagellate bloom (Lingulodinium polyedrum). The diversity of sites show that the IOP index is a suitable method to determine the phytoplankton bloom conditions.

Current variability by wave propagation in Todos Santos Bay, Baja California, Mexico

The temperature, velocity, and sea level fields for a summer climatological month (August) were analyzed using tridimensional and baroclinic model outputs in Todos Santos Bay (TSB), Baja California, Mexico. The numerical model was forced with wind (nonstationary), heat flux, and California Current System climatology on the open boundary. The 3- to 5-day current variability is related to a baroclinic wave traveling towards the northwest of the bay. Wave travel periodicity was due to the release of accumulated water from the Ensenada–Punta Banda Estuary (E–PBE) region. Local wind stress causes southeastward water flow and, given the TSB geometry, water accumulates in the E–PBE region. Weakening wind stress was the main cause of water release. In addition, complex empirical orthogonal function analysis found that outer TSB disturbances cause sea level variability.

The genus Spirontocaris Spence Bate, 1888 (Caridea, Decapoda, Thoridae) in western Mexico

Four species of Spirontocaris are known from a few records along the coast of the Baja California Peninsula, Mexico: S. prionoata (Todos Santos Bay), S. sica (between San Benito and Cedros Islands), S. snyderi (Cedros Island), and S. truncata (off San Carlos Point). During exploratory surveys off the west coast of the Baja California Peninsula, Mexico, two specimens of Spirontocaris holmesi Holthuis, 1947, and 143 of S. sica Rathbun, 1902 (10 males, 128 females, 2 ovigerous females, and 3 damaged specimens) were collected in benthic trawl and sledge. Both species are illustrated and described. The material of S. holmesi was collected in a single locality, at 220 m depth (known depth range is 150–300 m) and is the first record for western Mexico, while the material of S. sica was collected in five localities, from 710–1102 m depth (known range, 88–849 m), increasing significantly the number of specimens known for this species. Environmental data indicate that S. sica lives below the Oxygen Minimum Zone, in poorly oxygenated water (0.22 to 0.40 ml O2/l), in a temperature range of 4.38 to 5.81 °C. Sediments associated with this species are dominated by silt (>72% in 4 out of 5 localities), with organic carbon content of 18 to 52 mgCorg/g.

Patterns of Spatial Variation of Meiofauna in Sandy Beaches of Northwestern Mexico with Contrasting Levels of Disturbance

Despite the high abundance and diversity of meiofauna in sandy beach habitats, their patterns of spatial distribution have not been well characterized. This study analyzed the horizontal distribution of the intertidal meiofaunal community in sandy beaches of Todos Santos Bay (TSB), northwestern Mexico, and related it with levels of disturbance. Ten sandy beaches were sampled for meiofauna and sediment along the western coast of TSB at lower, mid, and upper levels of the intertidal. The meiofaunal community included five major groups viz. Amphipoda, Copepoda, Nematoda, Oligochaeta, and Polychaeta, and was mostly dominated by nematodes, regardless of the intertidal level. Meiofauna and nematode abundances differed significantly across the beach slope, increasing towards the upper level; this pattern varied along the shoreline, changing particularly where the beach was heavily modified due to costal development. Multivariate analyses significantly differentiated lower, mid, and upper levels of the intertidal, mostly due to differences in copepod abundance. Sediment grain size significantly differed among intertidal levels (i.e., smaller in the upper intertidal) and was negatively correlated with meiofaunal abundance. Moreover, meiofaunal abundance was negatively impacted by the degree of disturbance as highly urbanized/disturbed beaches of TSB showed lower meiofaunal abundance. As costal development continues to increase, findings from ecological surveys should play a pivotal role in characterizing and monitoring the health status of sandy beaches to aid in their management and conservation.

Treated wastewater effluent as a source of pyrethroids and fipronil at todos santos bay, Mexico: Its impact on sediments and organisms.

Pyrethroids are insecticides widely used to control pests and disease vectors in residential areas and agricultural lands. Pyrethroids are emerging pollutants, and their use is a growing concern because of their toxicity potential to aquatic organisms. Todos Santos Bay and the Punta Banda estuary, 2 coastal bodies located to the south of the Southern California Bight, were studied to establish a baseline of the current conditions of pollution by pyrethroids and fipronil. Eight pyrethroids, along with fipronil and its 2 metabolites, were determined in effluents from wastewater-treatment plants (n = 3), surface sediments (n = 32), and 3 locations with mussels (Mytilus californianus, n = 9). Bifenthrin, permethrin, and cypermethrin were the most common pyrethroids found in the study areas and were widespread in sediments, mussels, and wastewater-treated effluents. Fipronil and its metabolites were detected in mussels and wastewater-treated effluents only. Total pyrethroid concentrations in sediments ranged from 0.04 to 1.95 ng/g dry weight in the Punta Banda estuary (n = 13) and from 0.07 to 6.62 ng/g dry weight in Todos Santos Bay (n = 19). Moreover, total pyrethroids in mussels ranged from 1.19 to 6.15 ng/g wet weight. Based on the toxic unit data calculated for pyrethroids and fipronil for Eohaustorius estuarius and Hyalella azteca, little to no impact is expected to the benthic population structure. Environ Toxicol Chem 2017;36:3057-3064. © 2017 SETAC.

Anomalous hydrographic conditions off the northwestern coast of the Baja California Peninsula during 2013–2016

A succession of interannual warm events occurred in the Pacific during the 2013–2016 period, when positive thermal anomalies were detected. A broad region with abnormally warm waters in the northeastern Pacific Ocean was observed in 2013, which by 2015 had reached waters off Baja California (Mexico). In addition to the ongoing warming effect, early evidence of an El Niño event was detected in 2015. This paper analyzes hydrographic data measured at Todos Santos Bay and environs, as well as satellite-derived sea-level data, to characterize changes in the hydrographic conditions during the 2013–2016 period. The highest positive temperature anomalies (~5 ºC) were observed in September 2015, with a steep decline to neutral conditions in spring 2016. Records for the bay showed slight variations in hydrographic conditions during spring, highlighting the importance of local over remote forcings during this time of year. In autumn, by contrast, interannual signals prevailed over local processes. Satellite-derived sea-level data revealed an alongshore propagation of remote signals, identified as shallow coastal poleward flows.

Air-sea CO2 fluxes measured by eddy covariance in a coastal station in Baja California, México

The influence of wave-associated parameters controlling turbulent CO2 fluxes through the air-sea water interface is evaluated in a coastal region. The study area, located within the Todos Santos Bay, Baja California, México, was found to be a weak sink of CO2 with a mean flux of -1.32 µmol m-2s-1. The low correlation found between flux and wind speed (r = 0.09), suggests that the influence of other forcing mechanisms, besides wind, is important for gas transfer modulation through the sea surface, at least for the conditions found in this study. In addition, the results suggest that for short periods where an intensification of the wave conditions occurs, a CO2 flux response increases the transport of gas to the ocean.

The Relationship between Mollusks and Oxygen Concentrations in Todos Santos Bay, Baja California, Mexico

This study describes the relationship between mollusks, physicochemical properties of seawater, and sediments under natural conditions of low impact. Thirty-nine stations were sampled in October 1994 using a Van Veen grab (0.1 m−2). Temperature, salinity, and dissolved oxygen (DO) concentrations of bottom water were obtained with a CTD. Organic matter content and sediment grain analysis were determined. A total of 836 mollusks were collected. Gastropoda was the most abundant (52%) and diverse class with 27 genera, followed by Bivalvia with eight genera and Scaphopoda with only one genus. According to CCA analysis, dominant mollusks were significantly related with high DO concentrations.Donax,Natica,Acteocina,Bulla,Anachis,Odostomia, andCrucibulumcan be classified as sensitive genera because they were found mainly in high oxygen concentrations (3.1–5.6 mL L−1); on the other hand,Cardiomya,Nuculana,Laevicardium,Chione,Truncatella, andDentaliumcan be classified as tolerant genera (1.0–5.6 mL L−1). Todos Santos Bay hosts a diverse malacological fauna (36 genera); our results show that the dominant genera were mainly related to high dissolved oxygen concentrations. Mollusks can be a useful tool in environmental monitoring programs related with oxygen depletion in coastal areas.

Cadmium and phosphate variability during algal blooms of the dinoflagellate Lingulodinium polyedrum in Todos Santos Bay, Baja California, Mexico

Dinoflagellate algal blooms (DABs), with Lingulodinium polyedrum as the dominant species, have increased over the past few years in coastal areas off Baja California, Mexico. Vertical and temporal variability of particulate cadmium (Cdp), dissolved Cd (Cdd), PO43− and Cdd/PO43− were investigated during two intense DABs of L. polyedrum that occurred during the fall of 2011 and 2012 in Todos Santos Bay. Results were then, compared with data gathered in the absence of algal blooms during the autumn of 2013. In both algal blooms, L. polyedrum tended to be concentrated near the surface throughout the duration; however, during DAB 2011 the number of cells was twice as abundant ([10.0±8.0]×105cellsL−1) as in DAB 2012 ([5.0±4.4]×105cellsL−1). During DAB 2011, Cdp increased significantly (up to 1.02±0.99nmolkg−1) and was positively correlated with the cell abundance of L. polyedrum, suggesting that this dinoflagellate is able to assimilate and concentrate Cdd. Likewise, Cdd (up to 0.71±0.17nM) increased in the days of highest cell abundance, which could be attributed to uptake and subsequent regeneration of Cdd resulting from the remineralization of organic particulate matter produced during the bloom, as well as with the presence of organic ligands secreted by L. polyedrum that could keep Cdd in solution. During DAB 2011, dissolved Cdd/PO43− ratios exhibited high vertical and temporal variability in the upper 5m of the water column, but remained virtually constant near the bottom, suggesting a depth-dependent decoupling between these two dissolved components during the bloom development. Given the observed differences in the vertical and temporal variability of Cdd, Cdp, and PO43− between these two intense DABs, we propose the existence of an abundance threshold of approximately 106cellsL−1 of L. polyedrum above which Cd and PO43− significantly increased due to remineralization in coastal waters during the bloom development.

Presence of Sargassum horneri at Todos Santos Bay, Baja California, Mexico: Its Effects on the Local Macroalgae Community

To describe the annual cycle of Sargassum horneri in Mexican waters, we selected two sites differing in their degree of wave exposure and sediment type: Rincon de Ballenas (RB), and Rancho Packard (RP). From June 2009 to April 2010 we followed the seasonal changes in S. horneri density and biomass along two intertidal transects per site. The effects of this non-indigenous species on the local macroalgae community were assessed by comparing their species composition, density, biomass, species richness, and diversity index in quadrats with and without S. horneri. There were significant differences in S. horneri density and biomass between sites (P < 0.001). At RB the invasive alga density average was 2 ± 0.94 individual m-2, with a mean biomass of 4 ± 0.95 g DW m-2. At RP, S. horneri density average was 10 ± 0.96 individual m-2, and mean biomass of 102 ± 0.97 g DW m-2. At RB, the invasive alga promoted a significant reduction in the four selected structural variables, and the corticated macrophytes and the foliose functional forms were severely reduced. At RP, there were only marginally significant effects (P = 0.06) of S. horneri presence on the local macroalgae community, and higher density, biomass, and diversity values were found when S. horneri was present. Most of the functional forms were found, even if the invasive alga was present. At both locations, the highest biomass corresponded to the articulated calcareous functional form. These contrasting results could be due to the fact that the native macroalgae community has already been altered by the early invasion of S. muticum, with the most resilient species and functional forms remaining in place. One of the most important changes we noticed is the severe reduction of the canopy forming species at both sites.

Seasonal behavior of dissolved cadmium and Cd/PO4 ratio in Todos Santos Bay: A retention site of upwelled waters in the Baja California peninsula, Mexico

This work analyzes the spatial and seasonal variability of dissolved cadmium (Cdd) and the cadmium to phosphate ratio (Cd/PO4) in surface waters of Todos Santos Bay (TSB), a semi-enclosed bay within the upwelling zone of the Baja California peninsula (Mexico). The waters inside the bay (17.74±0.42°C) were on average warmer than the adjacent Pacific waters (14.67±0.52°C) indicating the retentive nature of circulation within TSB. Cdd and PO4 concentrations and Cd/PO4 ratios for this region are comparable to those reported for the California Current System. Cdd (0.30±0.036nM) and PO4 (0.97±0.061μM) concentrations outside of the bay presented a seasonal signal which was positively correlated with the local coastal upwelling index (CUI), suggesting that the magnitude of temporal variability of Cdd is partially controlled by the intensity of upwelling. In contrast, average Cdd (0.15±0.018nM) and PO4 (0.51±0.034μM) concentrations within the bay were approximately 50% less than those of the oceanic region, indicating that both elements are removed inside TSB. The dissolved Cd/PO4 ratio was not constant on a seasonal scale between the inside and outside of the bay, with higher values in the spring associated with upwelling conditions and greater phytoplankton biomass. Our findings show that there is a decoupling of Cd and PO4 cycles within TSB during the upwelling season, which is caused by an intensification of biological activity associated with the retention of water inside the bay. To explain the decoupling between Cd and PO4, we speculate that during the upwelling season this coastal system is temporarily relieved from micronutrient Zn limitation, causing an increase in the dissolved Cd/PO4 ratio due to preferential uptake of PO4 by phytoplankton. The seasonal variability of the dissolved Cd/PO4 ratios suggests that the Cd/Ca proxy must be used with caution to reconstruct past PO4 concentrations in surface waters of upwelling regions.

Lipophilic toxins in cultivated mussels (Mytilus galloprovincialis) from Baja California, Mexico

Here, we report different lipophilic toxins (LTs) detected by LC–MS/MS in Mediterranean mussels (Mytilus galloprovincialis) collected through 2012 in Todos Santos Bay, northwest Baja California, Mexico. The concentration of okadaic acid (OA), dinophysistoxin 2 (DTX2), and pectenotoxin 2 (PTX2) reached 500 μg kg−1 during July and increased to 1647 μg kg−1 in October. These toxins were associated with the presence of Dinophysis fortii and Dinophysis acuminata and a strong stratification of the water column. Other LTs present were yessotoxins, with a maximum concentration of 1080 μg kg−1 in June. Cyclic imines (13-desmethyl spirolide and gymnodimine) and azaspiracid 1 were also detected in the mussels but at low concentrations. Diarrhetic toxins concentrations evaluated by LC–MS/MS were compared with the results of two mouse bioassay protocols. Positive results were obtained with both MBA protocols in several samples that presented toxicities below 160 μg OA-eq kg−1, as estimated by LC–MS/MS results whereas other samples returned negative MBA results in samples with concentrations above this level. Therefore, analytical methods need to be applied to confirm the presence of regulated LTs. This is the first report of LTs in mussels cultivated in Mexico. The occurrence of these toxins represents an emerging problem in the region.

Spatial variability of internal waves in an open bay with a narrow steep shelf in the Pacific off NW Mexico

Small scale spatial patterns (<10km) in nearshore internal wave fields are rarely reported on, yet can have a large impact on nearshore mixing and productivity. In this study, the spatial pattern of internal wave characteristics were explored in Todos Santos Bay, Baja California (Mexico), using time series of temperature and currents from moored and towed thermistor chains and acoustic profiling current meters, as well as cross-shore transects with a towed undulating CTD system. Spectra of temperature and currents showed significant spatial variability within the bay, with the northern sector dominated by the internal tidally-forced semidiurnal signal, and the southern sector dominated by wind-forced, subinertial, baroclinic, diurnal fluctuations, which decreased with distance from shore. Semidiurnal internal tidal waves were generated by the barotropic tide at various sites on the continental slope to the west of the bay. They traveled toward the NE and reached the observation site in the northern part of the bay, after bouncing once or twice off the surface and the bottom. Despite the narrowness of the shelf, the semidiurnal internal tides at this site presented a first-mode structure, although not completely formed at times. On average, the semidiurnal internal waves had a ~9km wavelength, traveled in the form of an arc, and propagated with a phase velocity of ~20cm/s. When they reached shallow waters near the coast, they disintegrated rapidly into groups of short, nonlinear internal waves, with 15–20m amplitudes, 5–20min periods, and 50–200m wavelengths. The spatial patterns found in this study are most likely due to variability in distance from generation sites, complex bottom topography, and small scale (<10km) spatial variability in meteorological conditions such as winds.

Winter and Summer Evaluation of Bacteriological Water Quality at Recreational Beaches along Todos Santos Bay, Baja California, Mexico

Water bacteriological qualities of 22 recreational beaches in Ensenada Bay, Baja California, Mexico were analyzed during the summer and winter of 2008. Total and fecal coliforms as well as enterococci bacteria were used as pollution indicators. Results showed that bacteria concentrations were higher in winter than summer, associated with Southern California rainy season. Bacteria loads in winter exceeded both the daily and monthly standards showing a clear effect of storm water runoff in the quality of Todos Santos Bay recreational beaches. Statistical analysis showed significant differences between bacteria concentration during summer and winter. The general behavior of the indicators based on daily and monthly standards from high to low was enterococci > FC > TC> total/fecal ratio. Water discharged from 3 sewage treatment plants were responsible for the pollution observed at stations, when the uptake capacity of plants exceeded the storage. During summer pollution was due to non-programmed discharges from sewage treatment plants.

Circulation in the deep canyon at the entrance to Todos Santos Bay, México, Is there a deep net outflow?

A numerical model was used to investigate the deep circulation in a canyon of Todos Santos Bay, México. The deep canyon current at the entrance of Todos Santos Bay from a numerical model is compared with the annual averaged outflow from observations below 150m. The model result suggests that this reported outflow is part of an anticyclonic eddy, but more studies are required, both from numerical models and from observations, to know the circulation in that area.

Bioremediation of Hexadecane and Diesel Oil is Enhanced by Photosynthetically Produced Marine Biosurfactants

In the coastal environment of the Todos Santos Bay (Ensenada BC, Mexico), the sport fishing dock is chronically polluted due to frequent anthropogenic activity. The presences of aliphatic hydrocarbons in surface hydrocarbon-rich wastewater from this Bay reflect the differences in industrial and domestic pollutant activities. In this research, the bioprospection and screening of indigenous microbial mats led to the isolation of a strain of Phormidium sp. able to produce marine surface-active biosurfactants, which in turn contributed to bioremediate the levels of hexadecane and diesel. Field studies could corroborate the bioremediation potential of this strain. Our studies demonstrated that the marine cyanobacteria Phormidium sp. remove hexadecane (45%) and diesel oil (37%) from aqueous phase when grown in real seawater enriched with nutrients and in presence of these hydrocarbons within 10 days. The partially purified surface-active agents produced by Phormidium biodisk contributed to enhance the removal potential of this strain for hexadecane and diesel. In axenic cultures, the monospecific cyanobacterium Phormidium structured in biodisks mats exhibited degradative capacity on hydrocarbons in the range of C10–C28 carbon atom number in autotrophic conditions. The photoautotrophic growth of the biodisks of Phormidium has been registered by the presence of photosynthetically produced pigments markers, which partially are genre specific features, viz, phycocyanine, phycoerythrin as well as zeaxanthin and other important carotenoids and chlorophylls. Moreover, photosynthetically produced oxygen is believed played an important role in biodegradation of hexadecane and diesel oil. The obtained results indicate, a high removal potential of Phormidium and an environmental safe alternative for mitigating oil pollution seashores, by the joint action of photosynthetically produced exopolysaccharides type biosurfactants.

Antitumor activity of Actinobacteria isolated in marine sediment from Todos Santos Bay, Baja California, Mexico

Se realizo el estudio de la bioactividad de las Actinobacterias cultivables a partir de sedimento marino de la Bahia de Todos Santos, Mexico, y se identificaron mediante las secuencias del gen 16S ARNr. Las cepas bacterianas fueron cultivadas en 1 L de medio liquido A1 y se constato su crecimiento en presencia de agua de mar. Los extractos organicos de los cultivos se extrajeron con Amberlita XAD-7 eluida con acetona. Los extractos fueron separados por cromatografia en gel de silice C-18. Los extractos crudos y las fracciones se probaron contra celulas de cancer de colon HCT-116. En total, 26 cepas fueron cultivadas e identificadas, divididas en 10 unidades taxonomicas operacionales (UTOs) con 100% de identidad de sus secuencias, representando tres familias del orden Actinomycetales, pertenecientes a los generos Streptomyces (77%), Micromonospora (20%) y Nocardia (3%); 6 de estos UTOs no habian sido reportados previamente. Diecinueve por ciento de los extractos crudos del genero Streptomyces mostraron actividad citotoxica en un rango de IC50 de 69,0 a ≤ 0,076 mg·-1. Las fracciones mas activas contenian los compuestos monactin y derivados de pamamicina, los cuales fueron identificados por su peso molecular y sus patrones de fragmentacion.

Relationship between metal enrichments and a biological adverse effects index in sediments from Todos Santos Bay, northwest coast of Baja California, México

In 1992 and 2004, heavy metals concentrations were measured in surficial sediments from Todos Santos Bay, located in Ensenada, Baja California, Mexico. The aim was to search for relationships between metal enrichment factors and a biological adverse effects index. Unlike Ni, the elements Cd, Cu and Zn showed significant correlations (p<0.05) between enrichment factors and the biological adverse effects index. Cu showed a 0.74:1 relationship, which means that any enrichment above 0.74 could represent biological adverse effects. On the other hand, Cd and Zn enrichments must be >5.5 and >1.5, respectively, in order for the sediments to be considered toxic. In general, data showed that most of the metal concentrations in Todos Santos Bay sediments could not cause adverse effects to biota. Only Ensenada’s harbor and the zone next to a dredging dumping site showed metal enrichments that could be toxic.