Francisco Flores-Verdugo

Shrimp aquaculture development and the environment in the Gulf of California ecoregion

Beginning in the middle of the 1980s, the Gulf of California ecoregion experienced a boom in shrimp aquaculture and became the second largest producer in the western hemisphere. The moderated, but continual development of shrimp farming, in conjunction with municipal and agriculture effluents has been accompanied by concern about: (a) depletion of fishing stocks, (b) reduction of mangrove forest, (c) frequent harmful algal blooms in coastal waters and shrimp ponds, and (d) water quality deterioration. We demonstrate that environmental degradation resulted from a conjunction of factors including agriculture, untreated municipal effluents, shrimp aquaculture, increasing number of fishermen, and an absence of an effective regulatory program. We recommend the immediate implementation of an integrated coastal management program to protect the integrity of the coastal ecosystems and operate upon the principle of environmental sustainability for the different economic activities including shrimp aquaculture.

Mangrove ecology, aquatic primary productivity, and fish community dynamics in the Teacapán-Agua Brava lagoon-estuarine system (Mexican Pacific).

Aquatic primary productivity, mangrove ecology, and fish community dynamics were investigated in the Teacapán-Agua Brava lagoon-estuarine system, the most extensive mangrove ecosystem on the Pacific coast of Mexico with three species of mangroves distributed heterogeneously (Laguncularia racemosa, Rhizophora mangle, andAvicennia germinans). Tree density was 3,203 trees ha−1 and basal area was 14.0 m2 ha−1. Litterfall was 1,417 g m−2 yr−1, characteristic of a productive riverine forest. The degradation constant forLaguncularia racemosa leaves varied from 1.71 to 4.7 yr−1 and mean annual net aquatic productivity was 0.41 g C m−3 d−1. There were high concentrations of humic substances (up to 150 mg l−1) early in the wet season. Seasonal variations of the above parameters seemed closely related to the ecology of fish populations. There were 75 fish species distributed in two principal assemblages associated with wet and dry seasons. Diversity and biomass analysis indicated 18 dominant species. Total biomass of the community in this coastal system was estimated at 10 g wet wt m−2. The highest biomass occurred in the wet season. The most common fish species wereMugil curema, Achirus mazatlanus, Galeichthys caerulescens, Arius liropus, Diapterus peruvianus, Lile stolifera, Centropomus robalito, andEucinostomus sp., all of which have fishery importance. Primary productivity and fish community ecology are controlled by habitat characteristics, river discharge, and climatic seasonality.

Phytoplankton production and seasonal biomass variation of seagrass,Ruppia maritima L., in a tropical Mexican lagoon with an ephemeral inlet

Plankton metabolism andRuppia maritima biomass were measured seasonally during 1982–83 in El Verde Lagoon, a small coastal lagoon with an ephemeral inlet on the Pacific Coast of Mexico. Total net aquatic primary production was 521 g C m−2 y−1. The water column was slightly heterotrophic, with an annual P/R ratio of 0.89. Our analysis indicates that tropical and subtropical coastal lagoons with restricted or seasonal inlets have generally higher net aquatic primary productivity levels than lagoons with permanently open inlets. We hypothesize that this is due to retention of nutrients and plankton stocks during the dry season. The seasonal pattern of water column metabolism was related to rainfall and riverflow, with higher values generally occurring during the wet season. Net production and respiration were about three times lower during the 1982 dry season as compared to the 1983 dry season which received considerable rains due to abnormal climatic conditions. The biomass ofR. maritima ranged from zero to 620 g dry wt m−2. Growth occurred only during the dry season and there were two distinct biomass peaks representing two separate crops. The second crop was heavily epiphytized with nitrogen-fixing algae. There was an apparent succession in dominance of water column productivity over the year, withRuppia dominating during the dry season and phytoplankton more important during the wet season.

Forest structure, productivity and species phenology of mangroves in the La Mancha lagoon in the Atlantic coast of Mexico

We described, through a vegetation profile, the forest structure (density, basal area, tree height, and species composition), the productivity dynamics (based on litterfall) and the species phenology of distinct physiognomic types of mangroves in three locations of the La Mancha lagoon system in Veracruz, Mexico, during a complete annual cycle. We also evaluated the microtopography and ground water salinity along the profile and their relationship with forest structure and productivity. The South location showed four physiognomic types, whose forest attributes decreased as they were farther from the lagoon shore. Productivity and environment variables significantly varied among these physiognomic types. The Center location had two physiognomic types; there were significant differences in productivity and microtopography among these types, but not in salinity. The North location included two fragments of a basin forest type, and a pasture among them; productivity significantly varied among these forests, but microtopography and salinity were statistically similar. All study sites showed the following behavior: (1) as forest structure decreased, productivity also decreased and the dominant species changed. (2) As water salinity decreased, species dominance changed and productivity increased. Reproductive structures showed a notorious seasonality during the year in all species, except in R. mangle, which showed a permanent flower and propagules production. A. germinans reproduced only in the rainy season (August and September), because of their life history characteristics, whereas L. racemosa reproduced during the months of February and March as a response of the direct entrance of the water discharges, enriched with nutrients, that come from the sugar cane and rice crops. The South location was a relatively well conserved area, whereas the two other sites showed evidences of anthropic disturbances.

Examining Local Ecological Knowledge of Hurricane Impacts in a Mangrove Forest Using an Analytical Hierarchy Process (AHP) Approach

Abstract To examine the observations of fishermen regarding the impact of a hurricane on a mangrove forest of the Mexican Pacific, twenty-two structured interviews using an Analytical Hierarchy Process (AHP) approach were conducted in four villages of the Teacapán-Agua Brava lagoon-estuarine system. The local fishermen were asked to assess the likelihood that a mangrove tree would not survive a hurricane based on three attributes: main stem condition, diameter of main stem and species. The results suggest a high degree of consistency amongst the villages and with the observations of a previous investigation using the traditional scientific data collection methods. With few exceptions, the fishermen indicated that large diameter trees were the most susceptible to hurricanes. Conversely, that black mangrove (Avicennia germinans) and an intact main stem condition would indicate a better likelihood of surviving such an event. From the results of this investigation, it is suggested that the use of the AHP method can facilitate in the collection and interpretation of local ecological knowledge by scientists. Moreover, the output of this procedure, the vector of weights, can be used for comparison with scientific data collected by traditional means and for comparison with the observations of local peoples from other geographical locations.

The Use of Multipolarized Spaceborne SAR Backscatter for Monitoring the Health of a Degraded Mangrove Forest

Abstract To determine whether multipolarized spaceborne synthetic aperture radar could be used to monitor the health of a mangrove forest, leaf area index, as well as other biophysical parameter data, from stands dominated by white mangrove (Laguncularia racemosa) and located within a degraded mangrove forest were examined in relation to backscatter coefficients from ENVISAT synthetic aperture radar scenes. The results indicate that polarization and, to a lesser extent, incident angle play a significant role in the ability to estimate both leaf area index and mean tree height. No significant linear coefficients of determination were observed between the recorded parameters and the backscatter coefficient from any of the copolarized scenes. With regards to leaf area index, r2 values of 0.82 and 0.73 were calculated for the cross-polarized data at two incident angles. For mean tree height, the linear coefficient of determination was much higher for the smaller incident angle data than for the larger incident angle data. No significant relationships were identified for stem density, basal area, or mean diameter at breast height. It is postulated that the inability of the copolarized ENVISAT advanced synthetic aperture radar data to differentiate between dead mangrove stands and healthy ones is the result of equally high backscatter resulting from strong scattering from trunk–ground double bounce and crown volume, respectively.

Spectral response to varying levels of leaf pigments collected from a degraded mangrove forest

Mangrove forests are being removed or degraded at an alarming rate, even though they play a vital role in the sustainability of tropical coastal communities. Many of these forests are identified as degraded based on observable changes in their leaves (e.g., density, size, color, etc.). Of these, color can be considered one of the most important indicators of degradation because changes in the spectral response may be indicative of changes in the leaf pigment content. In this investigation, hyperspectral laboratory techniques were applied to examine potential relationships between the mangrove leaf spectral response and three leaf pigments: chlorophyll a, chlorophyll b, and total carotenoid content. Using an ASD spectroradiometer, the spectral reflectance of leaf samples were collected from poor condition, dwarf and healthy black (Avicennia germinans) and from healthy and poor condition red (Rhizophora mangle) mangroves located in a degraded mangrove system of the Mexican Pacific. A subset of 150 representational leaves was then used for pigment content analysis. The results indicate significant relationships between the spectral response and the levels of chlorophyll a, b, and total carotenoid content contained in the leaves. In particular, wavebands at the red edge position were shown to be the best predictors of the pigment contents. The results also indicate that vegetation indices do not necessarily improve the ability to predict these constituents. Finally, the red edge position was found to be significantly different between the healthy and poor condition mangroves ( P = 0 ), with the healthy mangroves having longer wavelengths associated with the red edge position.

Separating Mangrove Species and Conditions Using Laboratory Hyperspectral Data: A Case Study of a Degraded Mangrove Forest of the Mexican Pacific

Given the scale and rate of mangrove loss globally, it is increasingly important to map and monitor mangrove forest health in a timely fashion. This study aims to identify the conditions of mangroves in a coastal lagoon south of the city of Mazatlan, Mexico, using proximal hyperspectral remote sensing techniques. The dominant mangrove species in this area includes the red (Rhizophora mangle), the black (Avicennia germinans) and the white (Laguncularia racemosa) mangrove. Moreover, large patches of poor condition black and red mangrove and healthy dwarf black mangrove are commonly found. Mangrove leaves were collected from this forest representing all of the aforementioned species and conditions. The leaves were then transported to a laboratory for spectral measurements using an ASD FieldSpec® 3 JR spectroradiometer (Analytical Spectral Devices, Inc., USA). R2 plot, principal components analysis and stepwise discriminant analyses were then used to select wavebands deemed most appropriate for further mangrove classification. Specifically, the wavebands at 520, 560, 650, 710, 760, 2100 and 2230 nm were selected, which correspond to chlorophyll absorption, red edge, starch, cellulose, nitrogen and protein regions of the spectrum. The classification and validation indicate that these wavebands are capable of identifying mangrove species and mangrove conditions common to this degraded forest with an overall accuracy and Khat coefficient higher than 90% and 0.9, respectively. Although lower in accuracy, the classifications of the stressed (poor condition and dwarf) mangroves were found to be satisfactory with accuracies higher than 80%. The results of this study indicate that it could be possible to apply laboratory hyperspectral data for classifying mangroves, not only at the species level, but also according to their health conditions.

Accretion rates in coastal wetlands of the southeastern Gulf of California and their relationship with sea-level rise

Sea-level rise (SLR) is one of the most conspicuous examples of the environmental impact of recent climate change. Since SLR rates are not uniform around the planet, local and regional data are needed for proper adaptation plans. 210Pb-dated sediment cores were analyzed to determine the trends of sediment accretion rates (SARs) at three tropical saltmarshes in the Estero de Urias lagoon (Gulf of California, Mexico), in order to estimate the SLR trends during the past ~100 years, under the assumption that these ecosystems accrete at a similar rate to SLR. A chemometric approach, including multivariate statistical analysis (factor analysis) of geochemical data (including δ13C; δ15N; C/N ratios; and Br, Na, and Cl as proxies for marine transgression) was used to identify the marine transgression in the sediment records. Based on core geochemistry, only one of the three cores provided a long-term record attributable to marine transgression. SLR trends, estimated from SARs, showed increasing values, from a minimum of 0.73 ± 0.03 mm yr−1 at the beginning of the 20th century and up to 3.87 ± 0.12 mm yr−1 during the period 1990–2012. The estimated SLR trend between 1950 and 1970 was comparable to the tide gauge records in Mazatlan City for the same period. Results showed the caveats and strengths of this methodology to reconstruct decadal SLR trends from the sedimentary record, which can be used to estimate long-term SLR trends worldwide in regions where monitoring data are scarce or absent.

Ecology of Callinectes arcuatus and C. bellicosus (Decapoda, Portunidae) in a coastal lagoon of northwest Mexico

Some ecological aspects of the swimming crabs, Callinectes arcuatus and C. bellicosus are presented. Specimens were collected with a trawl net, both day and night, on a monthly basis from March 1998 to February 2000 in a coastal lagoon in northwest Mexico. A total of 1235 specimens were captured, C. bellicosus (n = 878) (abundance 0.5 to 60 ind. ha-1) was more abundant than C. arcuatus (n = 357) with an abundance from 0 to 38 ind. ha-1 during the study period. Both species were more abundant at night and usually were found in conjunction with macroalgae. Salinity (32 to 40‰) tended to favour the dominance of C. bellicosus over C. arcuatus (2.4 : 1) and the water temperature appeared to govern the breeding season (21 to 32°C). For both species, the breeding season runs from March until September (spring-summer), the recruitment of juveniles occurs during January and February (winter), and the lowest abundance of both species is found during October and November (fall). For both species, ovigerous females were observed in the mouth of the lagoon, and juveniles were found in the lagoons interior parts. The authors think that the observed ecological patterns of the species could be extrapolated to other coastal lagoons with a similar climate, oceanography, and geomorphology.