Lake Izabal Research Articles

Characteristics and spatial identification of Antillean manatee (Trichechus manatus manatus Sirenia: Trichechidae) strandings in Guatemala

Introduction: Marine mammal strandings can be used to determine the impacts of anthropogenic activity on the species survival, population health, and levels of environmental pollution in ecosystems. In addition, these data can help design conservation and management strategies as well as identify priority areas for the species. The West Indian manatee (Trichechus manatus) is listed as endangered throughout its range. In Guatemala, it is distributed along the Caribbean coast. Anthropogenic activities appear to be having a direct pressure on the species, affecting the status of the population.
 Objective: The general purpose of this study was to analyze the 30 years of documented manatee stranding reports available for Guatemala. Two specific objectives were defined to: 1) conduct a spatial analysis of manatee strandings to identify the areas of high stranding concentration, and 2) determine whether there were sex differences in the number of strandings.
 Methods: Characteristics and areas of concentration of manatee strandings were described along the Caribbean coast between 1992 to 2022. Sites with the highest probable density of strandings were identified using a Kernel density analysis. We compared the number of stranding events that occurred in each protected area that included manatees in their management plans and each municipality of Izabal. We determined whether there were sex differences in the number of stranded manatees. We use the potential biological removal to estimate the maximum number of manatees that can be removed from the population due to anthropogenic causes without negatively impacting species survival.
 Results: Forty-three manatee stranding events were recorded throughout the species’ range in Guatemala (48 total individuals). The sites with the highest predicted density of strandings were Santo Tomás de Castilla bay, followed by Lake Izabal (including the limits of the Refugio de Vida Silvestre Bocas del Polochic) and Parque Nacional Río Dulce. The majority of the cases were registered in protected areas (60 %). Estimates of potential biological removal were equivalent to less than one manatee per year, which was exceeded by the annual average of stranded manatees recorded (three manatees).
 Conclusions: Anthropogenic activities cause mortality of manatees in this region, despite the implementation of protected areas. Poaching was identified as the main cause of manatee mortality in Guatemala. The implementation of management strategies focused on minimizing threats to the species, based on the application of environmental legislation and environmental awareness, is essential. The creation and implementation of a protocol for the stranding of marine mammals on the Caribbean coast of Guatemala is necessary, in order to obtain standardized records of these events and conduct rescue efforts and releases when possible.

Planning for the Lake Izabal Basin Research Endeavor (LIBRE) continental scientific drilling project in eastern Guatemala

Abstract. As Earth's atmospheric temperatures and human populations increase, more people are becoming vulnerable to natural and human-induced disasters. This is particularly true in Central America, where the growing human population is experiencing climate extremes (droughts and floods), and the region is susceptible to geological hazards, such as earthquakes and volcanic eruptions, and environmental deterioration in many forms (soil erosion, lake eutrophication, heavy metal contamination, etc.). Instrumental and historical data from the region are insufficient to understand and document past hazards, a necessary first step for mitigating future risks. Long, continuous, well-resolved geological records can, however, provide a window into past climate and environmental changes that can be used to better predict future conditions in the region. The Lake Izabal Basin (LIB), in eastern Guatemala, contains the longest known continental records of tectonics, climate, and environmental change in the northern Neotropics. The basin is a pull-apart depression that developed along the North American and Caribbean plate boundary ∼ 12 Myr ago and contains > 4 km of sediment. The sedimentological archive in the LIB records the interplay among several Earth System processes. Consequently, exploration of sediments in the basin can provide key information concerning: (1) tectonic deformation and earthquake history along the plate boundary; (2) the timing and causes of volcanism from the Central American Volcanic Arc; and (3) hydroclimatic, ecologic, and geomicrobiological responses to different climate and environmental states. To evaluate the LIB as a potential site for scientific drilling, 65 scientists from 13 countries and 33 institutions met in Antigua, Guatemala, in August 2022 under the auspices of the International Continental Scientific Drilling Program (ICDP) and the US National Science Foundation (NSF). Several working groups developed scientific questions and overarching hypotheses that could be addressed by drilling the LIB and identified optimal coring sites and instrumentation needed to achieve the project goals. The group also discussed logistical challenges and outreach opportunities. The project is not only an outstanding opportunity to improve our scientific understanding of seismotectonic, volcanic, paleoclimatic, paleoecologic, and paleobiologic processes that operate in the tropics of Central America, but it is also an opportunity to improve understanding of multiple geological hazards and communicate that knowledge to help increase the resilience of at-risk Central American communities.

Distinct Modes of Aged Soil Carbon Export in a Large Tropical Lake Basin Identified Using Bulk and Compound‐Specific Radiocarbon Analyses of Fluvial and Lacustrine Sediment

AbstractThe 14C content of sedimentary organic matter (OM) and specific organic molecules provide valuable information on the source and age of OM stored in sediments, but these data are limited for tropical fluvial and lake sediments. We analyzed 14C in bulk OM, palmitic acid (C16), and long‐chain n‐alkanoic acids (C24, C26, and C28), within fluvial and lake sediments in the catchment of Lake Izabal, a large tectonic lake basin in Guatemala. We combined these measurements with bulk and compound‐specific δ13C measurements, as well as sediment organic carbon to nitrogen (OC:N) ratios, to understand the source and age of sedimentary OM in different regions of the lake catchment. Most fatty acid and bulk OM samples were characterized by pre‐modern carbon, indicating important input of aged carbon with residence times of hundreds to thousands of years into sediments. We identified two mechanisms leading to aged carbon export to sediments. In the high‐relief and deforested Polochic catchment, older OM and fatty acids are associated with low % total organic carbon (TOC) and low OC:N, indicating aged OM associated with eroded mineral soil. In the smaller, low‐relief, and largely forested Oscuro catchment, old OM and fatty acids are associated with high %TOC and high OC:N ratios, indicating export of undegraded aged plant biomass from swamp peat. The age of bulk OM and fatty acids in Lake Izabal sediments is similar to the ages observed in fluvial sediments, implying that fluvial input of aged soil carbon makes an important contribution to lake sediment carbon reservoirs in this large tropical lake.

A millennium of anthropic and climate dynamics in the Lake Izabal Basin, eastern lowland Guatemala

Modern precipitation gradients across the Maya region in Central America result in a diverse vegetational mosaic that varies from scrub forest to rainforest. In this region, evidence of past changes in the distribution of vegetation indicates two main patterns: i) a Holocene long-term trend towards a more seasonal forest, and ii) sharp changes in vegetation cover resulting from human occupation. The history of vegetation in moister areas of the Maya region, however, has been mostly extrapolated from studies carried out in the Yucatan Peninsula. We reconstructed the paleoenvironmental and paleoecological dynamics of the last ∼1300 years in the Lake Izabal Basin, one of the wettest areas within the Maya region. Palynological and geochemical evidences indicate that from ∼650–1150 CE, vegetation assemblages were dominated by disturbance taxa, under relatively low erosion in the catchment area. This pattern probably resulted from anthropogenic activities during the Terminal Classic Period (800–950 CE) combined with the dry and more seasonal conditions of the Medieval Climate Anomaly. The record from 1150 to 1400 CE points to an increase in moisture availability with a change towards a forested landscape. From 1400 to 1950 CE, geochemical data indicate lower precipitation, while the vegetation appears less fragmented and a mature forest developed. Such pattern probably emerged from lower evapotranspiration associated with the Little Ice Age (1350–1850 CE) favoring vegetation recovery. During the last 1300 years, vegetation change in the Lake Izabal Basin parallels that of the Yucatan Peninsula, with anthropogenic influences and moisture availability exerting first- and second-order controls on vegetation turnover, respectively.

New estimates of the magnitude of the sea-level jump during the 8.2 ka event

Abstract We analyzed sediment cores from coastal Lake Izabal, Guatemala, to infer Holocene biogeochemical changes in the lake. At ca. 8370 calibrated yr B.P. (cal. yr B.P.), marine waters entered the lake, which presently lies ~38 km from the Caribbean coast. Temporal correlation between Early Holocene drainage of high-latitude Lakes Agassiz and Ojibway (in North America) and marine flooding of Lake Izabal suggests a causal link between the two processes. Our data indicate a relative sea-level jump of 2.60 ± 0.88 m, which is larger than previous estimates of sea-level rise during the 8.2 ka event. The inferred sea-level jump, however, cannot be explained solely by the volume of water released during drainage of Lakes Agassiz and Ojibway. Instead, we propose that previous studies underestimated the magnitude of Lakes Agassiz and Ojibway discharge, or that additional meltwater sources contributed to global sea-level rise at that time.

A progressively wetter early through middle Holocene climate in the eastern lowlands of Guatemala

Climate records from Central America and the Caribbean region reveal considerable spatiotemporal complexity in precipitation variability, with multiple hypotheses explaining the likely ocean-atmosphere processes influencing precipitation in the region. Here we report on findings from a 760-cm long sediment core from Lake Izabal, eastern Guatemala that affords insight on regional hydroclimate change over the last ∼9,500 years. We utilized a radiocarbon-based age-depth model integrated with lithological, XRF elemental abundances, and principal component analyses to infer changes in erosion/precipitation, lake productivity, and lake water chemistry. Abundance of elements commonly associated with terrigenous sources increase from the early to the latest mid-Holocene, from ca. 9,500 to ca. 4,800 calibrated years before present (cal yr BP), suggesting a progressive increase in erosion/precipitation. This is followed by relatively stable and high erosion/precipitation conditions until ca. 1,200 cal yr BP, with an abrupt decrease in erosion/precipitation ∼1,200 years ago. Comparison of the Izabal record with other paleoclimate records from Central America and the Caribbean region indicates substantial heterogeneity in hydroclimate, even across relatively short distances, likely due to a combination of topographic complexity and the combined influences of Atlantic and Pacific basin ocean-atmosphere dynamics. Our results suggest that the progressive increase in boreal autumn insolation throughout the middle and late Holocene may have driven an increase in Caribbean sea-surface temperatures (SST) during the late wet season, leading to increased moisture availability through enhanced evaporation and greater precipitation amounts associated with zonal convergence and orographic uplift along the eastern coast of Central America. However, other nearby records demonstrate hydroclimate changes that are at least partially at odds with the Izabal record, indicating that the modern SST relationships with atmospheric circulation, including Intertropical Convergence Zone dynamics, and precipitation alone cannot be used as a framework for explaining hydroclimate variability across Central America during the Holocene.

Natural and anthropogenic sources of lead, zinc, and nickel in sediments of Lake Izabal, Guatemala

Sediments in Lake Izabal, Guatemala, contain substantial lead (Pb), zinc (Zn), and nickel (Ni). The lack of historical data for heavy metal concentrations in the sediments makes it difficult to determine the sources or evaluate whether inputs of metals to the lake have changed through time. We measured the relative abundances and concentrations of Pb, Zn, and Ni by X-Ray Fluorescence core scanning and by Inductively Coupled Plasma Optical Emission Spectrometry in three sediment cores to explore stratigraphic distributions of metals in the lake deposits. High amounts of Pb and Zn in the core taken near the Polochic Delta suggest that galena and sphalerite mining increased Pb and Zn delivery to Lake Izabal between ~1945 and 1965 CE. An up-core Ni increase in the core taken near a different mine on the north shore of Lake Izabal suggests that recent nickel mining operations led to an increase in Ni concentrations in the local sediments, but amounts in the other cores indicate that Ni is not widely distributed throughout the lake. Sediment cores from Lake Izabal are reliable recorders of heavy metal input to the lake, and were measured to establish background metal levels, which would otherwise be unavailable. Concentrations of Pb, Zn, and Ni in older, pre-20th-century Lake Izabal sediments reflect input from natural erosion of bedrock. Our results provide previously unavailable estimates of background metal concentrations in Lake Izabal before the onset of mining. These results are necessary for future monitoring related to mining contamination of the lake ecosystem.

The role of the Polochic Fault as part of the North American and Caribbean Plate boundary: Insights from the infill of the Lake Izabal Basin

AbstractThe Lake Izabal Basin in Guatemala is a major pull‐apart basin along the sinistral Polochic Fault, which is part of the North American and Caribbean plate boundary. The basin infill contains information about the tectonic and sedimentological processes that have imparted a significant control on its sedimentary section. The inception of the basin has been linked to the relative importance of the Polochic Fault in the tectonic history of the plate boundary; yet, its sedimentological record and its inception age have been poorly documented. This study integrates diverse datasets, including industry reports, well logs and reports, well cuttings, vintage seismic data, outcrop observations and geochronological data to constrain the initial infill and age of inception of the basin. The integrated data show that during the Oligocene–Miocene, a marine carbonate platform was established in the region which was later uplifted and eroded in the early Miocene. The fluvial–lacustrine deposits above this carbonate platform are part of the initial infill of the basin and are constrained with zircon weighted‐mean 206Pb/238U ages of 12.060 ± 0.008 from a volcanic tuff ~30 m above the unconformity. Sandstone, mudstone and coal dominate the interval from 12 to 4 Ma, with an increase in conglomerate correlating to the uplift of the Mico Mountains and San Gil Hill at 4 Ma. Fault switch activity between the Polochic and Motagua faults has been hypothesized to explain total offset along the Polochic Fault and the geologic and geodetic slip rates along the two faults. The 12 Ma age determined for the initial infill of the basin confirms this hypothesis. Consequently, our study confirms that at ~12 Ma the Polochic Fault served as the main fault of the plate boundary with inferred slip rates ranging from 13 to 21 mm/yr with a strong possibility that the Polochic Fault was, at some point between 15 Ma and 7 Ma, the only active fault of the plate boundary. The results of this study show that tectonic records preserved in sediments of strike‐slip basins improve the understanding of the relative significance of individual faults and the implications with respect to strain partitioning throughout its tectonic history.

Recent onset of eutrophication in Lake Izabal, the largest water body in Guatemala

Recent human population growth has contributed to the degradation of environmental resources in Guatemala. Since 1900, the population of the country grew from 17 million inhabitants. The watershed of Lake Izabal, eastern Guatemala, also experienced rapid population growth, and with it, development of intensive agriculture in areas adjacent to the lake. These recent demographic and land-use changes altered anthropogenic nutrient inputs to the water body, through delivery of raw sewage, and agricultural practices that include excessive use of fertilizers. Currently, Lake Izabal is marked by frequent algal blooms and associated fish-kill events. It also hosts a number of invasive, and in some cases, exotic plant and animal species. We used data from a sediment core collected in the western end of the lake to link past anthropogenic activities in the watershed to the deterioration of water quality and shifts in aquatic ecosystem functioning. We measured total organic carbon (TOC), total nitrogen (TN), and δ13C and δ15N of organic matter in a 137Cs- and 14C-dated sediment core from the Polochic Delta in Lake Izabal to infer past limnological changes. The core chronology indicates that 505 cm of sediment accumulated in only the last 370 years (~ 1.4 cm a−1). TOC and TN concentrations increased since about 1950, a time during which the TOC:TN ratio decreased, indicating a relatively greater contribution of phytoplankton to the sediment organic matter. Stratigraphic shifts in δ13C and δ15N indicate recent increasing inputs of raw sewage and fertilizer to the lake during the same time period. Lake Izabal, like many other water bodies in Guatemala, is starting to undergo cultural eutrophication, which probably accounts for the frequent algal blooms, proliferation of invasive species (e.g. Hydrilla verticillata), and decline in fish abundance.

Chinchaysuyoa, a new genus of the fish family Ariidae (Siluriformes), with a redescription of Chinchaysuyoa labiata from Ecuador and a new species description from Peru.

In recent years, morphological and molecular studies have improved our understanding about the relationships and classification schemes of the marine catfishes of the family Ariidae. A taxonomic issue that is still contentious concerns the limits and status of the freshwater Neotropical ariid diversity, in particular the species in the genus Potamarius. The delimitation of Potamarius is currently uncertain given the disjunct distribution of the species in Mesoamerica (Potamarius izabalensis, P. nelsoni and P. usumacintae, from Lake Izabal and Usumacinta River basins in Mexico to Guatemala) and Brazil (P. grandoculis, from coastal lakes in southeastern Brazil). The freshwater Arius labiatus and Hexanematichthys henni from the Peripa and Daule rivers in Ecuador that drain to the Eastern Pacific (EP), have also at times been listed as species inquirenda in Potamarius. Here, we redescribe Arius labiatus, redefine the taxonomic status of Hexanematichthys henni, as junior synonym of Arius labiatus, and describe a new species from Peru that is closely related to Arius labiatus. Based on morphological and molecular phylogenetic evidence, we also describe a new genus (Chinchaysuyoa) for the two South American species.

Sedimentary architecture, structural setting, and Late Cenozoic depocentre migration of an asymmetric transtensional basin: Lake Izabal, eastern Guatemala

Lake Izabal, located in eastern Guatemala, lies in an EW-trending basin located along the transform margin between the North American and Caribbean plates. This plate boundary consists of two main left-lateral, strike-slip faults known as the Polochic and Motagua Fault System (PMFS). The basin is a 100 × 20 km lens-shaped depression in which the lake occupies its eastern half. To the north, the basin is confined by a Principal Deformation Zone (PDZ) which is recognized in this area as the most important upper-crustal branch of the Polochic Fault. The eastern part of the basin has been uplifted and dissected, exposing the basin infill along the slopes of the Montaña del Mico. Analysis of a set of multichannel seismic reflection profiles, most of them acquired within the lake, combined with well and outcrop information, allowed to outline the structure and evolution of the basin and its stratigraphic architecture. The basin is strongly asymmetrical, both in cross and along-strike directions, and is filled up by Neogene to Quaternary sediments, with the deepest side of the basin being to the north, close and parallel to the PDZ. The base of the infill is a mid-Tertiary unconformity whose differential subsidence through time brought the basin to its present structural setting. Five main evolutionary stages are recognized based on seismo-stratigraphic and structural features, which are related to the development and activity of the bordering faults. Development of the basin began in its easternmost sector. A small half graben, tilted to the south, developed in response to the activity of an Oligocene (?) or Early-Middle Miocene growth fault. In the second stage (Late Miocene), the basin tilts to the north, causing the sedimentary sequences to thicken towards the northern PDZ. This stage is dominated by oblique extension, and by progressive migration of the basin depocenter towards the west. The third stage (Early Pliocene) records a strong acceleration of the strike-slip activity which causes a rapid westward migration of the depocenter. The fourth stage (Late Pliocene), although still dominated by regional transtension, is related to the development of a transpressional event along the eastern side of the basin, as evidenced by the occurrence of folds and reverse faults parallel to the northern bend of the Polochic Fault. During the fifth stage (Quaternary), the eastern part of the basin remains relatively quiescent while the western part undergoes subsidence with localized transtension, still related to the activity in this sector of the Polochic Fault. Left-lateral movement along the Polochic Fault caused the depocenter to migrate 75–80 km at different velocities, with slip rates ranging between 2.1 and 16.3 mm/yr. This study suggests that the Polochic Fault developed in the Early-Middle Miocene in connection to the deposition of the early sediments of the Izabal Basin, even though an older age (Oligocene?) could also be possible. To our knowledge, this is one of the best examples of sedimentary architecture documenting depocentre migration due to fault movement along a transform system.

Identificación taxonómica de especies Icticas de los ríos Polochic y Cahabón, de la vertiente del atlántico guatemalteco

Los ríos Polochic y Cahabón, son cuencas de la vertiente del atlántico guatemalteco. Sin embargo, estos sufren el impacto de contaminantes, ya que reciben desechos antropogénicos y aunque poseen la capacidad de soportar alteraciones mediante los procesos internos de autodepuración, la cantidad y calidad de los desechos introducidos puede superar su mecanismo de recuperación. Esto pone en peligro la existencia de la diversidad biológica presente en estos sistemas acuícolas, por lo anterior, se consideró importante la realización de la presente investigación, que consistió en la identificación taxonómica de peces óseos. La metodología empleada, fue la técnica de transectos, con muestreos aproximados de quince kilómetros. El proceso de captura se realizó mediante el uso de atarrayas, trasmallos, anzuelos, etc., durante los meses de mayo, junio y julio del año 2,000. Los ejemplares capturados se conservaron en una solución a base de formalina al diez por ciento, para posteriormente ser identificados en función de sus características morfológicas y merísticas. Los resultados obtenidos fueron la identificación de treinta especies de peces de la clase Osteichthyes, distribuidos en dieciséis familias, de las cuales diecisiete se encontraron en el río Polochic, cinco en el río Cahabón y ocho especies comunes para ambos ríos. Además de conocer el nombre científico de las mismas, se cuenta con el nombre vernáculo con el cual son conocidos estos teleósteos en los diferentes lugares de muestreo. Resalta el hecho de que la diversidad aumenta a medida que las cuencas se aproximan al lago de Izabal. Cabe mencionar, que algunas especies son introducidas lo que pone en peligro el equilibrio estos ecosistemas acuícolas. Desde el punto de vista zootécnico conocer la diversidad de especies ícticas, permitirá en futuras investigaciones evaluar el potencial productivo de cada una y la importancia alimenticia que representan para las familias del área rural.

Ecological linkages in a Caribbean estuary bay

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 533:29-46 (2015) - DOI: https://doi.org/10.3354/meps11342 Ecological linkages in a Caribbean estuary bay H. Andrade1,2,*, J. Santos1, M. J. Ixquiac3 1Norwegian College of Fishery Science, University of Tromsø, 9037 Tromsø, Norway 2Akvaplan-niva AS, Framsenteret, 9296 Tromsø, Norway 3Centro de Estudios del Mar y Acuicultura, Universidad de San Carlos de Guatemala, Guatemala 01012, Guatemala *Corresponding author: hector.andrade@akvaplan.niva.no ABSTRACT: Central America and the western Caribbean regions form a center of freshwater and marine biodiversity that is increasingly becoming the focus of ecological and evolutionary studies. We conducted an integrated ecological study of Amatique Bay, Guatemala, a major estuary lagoon connected to the low-lying Lake Izabal and to the Mesoamerican Reef System, and provide novel information for the management and conservation of similar systems across the Caribbean. Precipitation and wind regimes constitute important environmental drivers of ecosystem functioning, which partially compensate for the weak tidal-forcing that is characteristic of the Caribbean Sea. Seasonal peaks in temperature and precipitation were strongly correlated to the reproduction of marine, catadromous and estuarine fish species, suggesting that the ensuing increase in primary production provides larval fish with an abundant food source. Increased abundances of transient marine species were observed during the dry season, which may be explained by passive transport, feeding migration, or both, considering that prey may be more abundant inshore and that environmental conditions are dominated by higher salinity and stronger onshore winds during this period. Despite being a stopover site for many long-range migrating shorebird species, the Bay serves primarily as a resting place since it lacks extensive tides and tidal flats, and thus provides limited access to invertebrate prey. Furthermore, this sheltered environment, featuring abundant freshwater, seasonally high water clarity, and low tidal amplitude, is likely to provide good habitat for abundant seagrasses and manatees. The Lake Izabal-Amatique Bay complex demonstrates a wide range of teleconnections and connectivity among terrestrial, freshwater, and marine oceanic and reef ecosystems. Understanding the evolution and ecology underlying this highly connected system is required for the management of the multi-trophic, small-scale fisheries it sustains. KEY WORDS: Fisheries · Migratory shorebirds · Manatee · Life history · Environmental drivers · Tropical conservation · Evolution · Central America Full text in pdf format Supplementary material PreviousNextCite this article as: Andrade H, Santos J, Ixquiac MJ (2015) Ecological linkages in a Caribbean estuary bay. Mar Ecol Prog Ser 533:29-46. https://doi.org/10.3354/meps11342 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 533. Online publication date: August 06, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Status and the potential for extinction of the largetooth sawfish Pristis pristis in the Atlantic Ocean

ABSTRACT Sawfishes currently are among the most threatened elasmobranchs in the world. Only two species inhabit Atlantic waters: the largetooth sawfish (Pristis pristis) and the smalltooth sawfish (Pristis pectinata), both having suffered dramatic declines in their ranges. The goal of this study was to evaluate the status of P. pristis in the Atlantic, and estimate local extinction risk based on historical and recent occurrence records. In order to accomplish these goals, a thorough search for historical and recent records of P. pristis in the Atlantic was conducted, by reviewing scientific and popular literature, museum specimens, and contacting regional scientists from the species’ historical range. In total, 801 P. pristis records (1830–2009) document its occurrence in four major regions in the Atlantic: USA (n = 41), Mexico and Central America (n = 535), South America (n = 162), and West Africa (n = 48). Locality data were not available for 15 records. Historical abundance centres were the Colorado‐San Juan River system in Nicaragua and Costa Rica (and secondarily Lake Izabal of Guatemala), the Amazon estuary, and coastal Guinea‐Bissau. Currently, the species faces drastic depletion throughout its entire former range and centres of abundance. It appears to have been extirpated from several areas. The probability of extinction was highest in the USA, northern South America (Colombia to Guyane), and southern West Africa (Cameroon to Namibia). Currently, the Amazon estuary appears to have the highest remaining abundance of P. pristis in the Atlantic, followed by the Colorado–San Juan River system in Nicaragua and Costa Rica and the Bissagos Archipelago in Guinea Bissau. Therefore the protection of these populations is crucial for the preservation and recovery of the species. Copyright © 2013 John Wiley & Sons, Ltd.

Obituary: Passing of an Ecosystem Naturalist, Mark M. Brinson 1943–2011

Obituary: Passing of an Ecosystem Naturalist, Mark M. Brinson 1943–2011

New methods for the analysis of invasion processes: Multi-criteria evaluation of the invasion of Hydrilla verticillata in Guatemala

The study described in this article incorporates stakeholders’ views on aquatic invasion processes and combines expert analysis with information from field work into an evaluation exercise. Management scenarios are designed based on available technical data and stakeholders’ perceptions. These scenarios are evaluated using the Social Multi-Criteria Evaluation framework employing the NAIADE model. Two evaluations are carried out, technical and social. Social acceptance of different management scenarios, distribution of costs and benefits, and attribution of responsibility are discussed.The case study was carried out on Lake Izabal, a body of water connected to the Caribbean Sea in Northeastern Guatemala. In 2000, local fishermen reported the presence of an alien species in the lake, the macrophyte Hydrilla verticillata. Two years later, this alien species was established around the entire lakeshore, damaging the ecosystem, endangering native species and the subsistence of local inhabitants through impacts on transportation, fishing practices, and tourism.

Water volume variations in Lake Izabal (Guatemala) from in situ measurements and ENVISAT Radar Altimeter (RA-2) and Advanced Synthetic Aperture Radar (ASAR) data products

Summary The water storage variations in lakes affect their physical, chemical and biological processes. Besides, the water masses of these waterbodies reflect the balance of the rainfall and evaporation with surface and ground waters. The lake’s water volume is estimated combining water level variations with accurate bathymetry and shore topography maps. Lake Izabal is the largest waterbody of Guatemala (approximately 673.29 km 2 ). Its water volume has been estimated in the past but the volume variations are still unknown. The lake water level variations are monitored in situ since 2004, but regrettably accurate information about the bathymetry and shore topography is not available. The main objective of this study was to make a first estimate of the Lake Izabal water volume variations. To do this, we combined level variations and inundated area variations. The lack of accurate bathymetry and topography maps was overcame by using inundated area variations in the assumption that every level change reflects an inundated area response, depending on bathymetry and shore topography. The level variations were estimated from an in situ moored gauged in the lake and from the ENVISAT Radar Altimeter (RA-2). The inundated area variations were obtained using 12 ENVISAT Advanced Synthetic Aperture Radar (ASAR) images. Prior to the area estimates the lake’s shoreline was extracted making use of a chain of existing image processing algorithms. The correlation analysis between in situ lake levels and inundated area variations yielded a correlation coefficient of 0.9. The volume variations of the lake were then estimated on the dates of the acquired SAR images. Then, a group of rating curves relating level, area and volume were developed. In order to extend the area and volume estimates to the whole study time period (February 2003 to December 2006) the lake levels from the RA-2 dataset were entered to the rating curves. The estimated water volume variations of Lake Izabal range between 8271.2 × 10 6 m 3 (17th December of 2005) and 9018.15 × 10 6 m 3 (15th July of 2006) in agreement with the most recent estimation of the Lake Izabal water volume (8300 × 10 6 m 3 ). Regarding the inundated area variations, they range between 672.44 × 10 6 m 2 (17th December of 2005) and 677.2 × 10 6 m 2 (15th July of 2006) in agreement with the Guatemalan government information (673.29 km 2 ). The water volume, inundated area and water level fluctuations of the Lake Izabal show a strong seasonal signal with high stages during the rainy season (May–November) and low stages during the dry seasons (December–April). These results give valuable information for the Lake Izabal management and strengthen the idea of using remote sensing as a powerful and cheap complementary tool for hydrologic purposes.

Water level fluctuations derived from ENVISAT Radar Altimeter (RA-2) and in-situ measurements in a subtropical waterbody: Lake Izabal (Guatemala)

The use of remote sensing techniques in monitoring inland waters has become a powerful tool, considering the amount of ungauged waterbodies all over the world. The water mass balance is an essential subject to take into account in water management activities. The level changes of a lake surface are an indicator of the water mass balance of a basin since they reflect the water storage variations. Space borne altimeters have been successfully used in the last decade to measure lakes, rivers and wetland stages. This study presents the first analysis of Lake Izabal — the biggest lake of Guatemala (Central America) — water level fluctuations using altimetry data and in-situ measurements. Water level variations were obtained from Envisat Radar Altimeter (RA-2) Geophysical Data Records coupled with in-situ measurements. The analysis period included three complete years (2004 to 2006). The rainfall and temperature records over the catchment were analyzed considering that the amount of water feeding the lake, either by the tributaries and/or the groundwater, is driven by the climatic conditions over the lake's catchment. The results obtained show a good agreement between both, altimeter and in-situ datasets (correlation coefficient: 0.83 and rms error: 0.09 m). Lake Izabal water level fluctuations have a seasonal signal forced by the rainy and dry climate seasons in the region. An abrupt lake level rise was found in July 2006 which is correlated to abnormal precipitations in June. We found a connection between the higher/lower extreme values in the lake level variations with rainfall anomalies produced by regional climate changes forced by El Niño Southern Oscillation and the Tropical North Atlantic anomaly.

Fish abundance and community composition in native and non‐native plants following hydrilla colonisation at Lake Izabal, Guatemala

Abstract Fish community composition was assessed among six macrophyte habitats, including hydrilla, Hydrilla verticillata (L.F.) Royle, common native species (bulrush, Scirpus spp., muskgrass, Chara spp., eelgrass, Vallisneria americana Michx. and Illinois pondweed, Potamogeton illinoensis Morong) and no‐plants, to assess potential impacts of recent hydrilla colonisation on the littoral fish community at Lake Izabal, Guatemala. Fish biomass was significantly different among habitats, with hydrilla supporting the highest fish biomass. Fish density did not differ significantly among habitats. Total fish species richness was similar (12‐15 species) among habitats, but community composition changed with macrophyte presence. Biomass of mojarra, Cichlasoma maculicauda Regan, which supported the most important subsistence fishery at the lake, was significantly different among habitats and had the greatest biomass in the hydrilla habitat. Although hydrilla may adversely affect native plants, lake access and other uses, it provided useful fish habitat and likely was not detrimental to the Lake Izabal fish community composition.

A Social Analysis of the Bioinvasions of Dreissena polymorpha in Spain and Hydrilla verticillata in Guatemala

Human agency plays a key role in the processes of biological invasions. This comprises not only the human role in the configuration of driving forces or in the perception of the impacts, but also the conceptualization of alien species themselves as an environmental problem. This paper examines different stakeholders' positions in bioinvasion processes at different scales, and it looks at their relevance for the management of invasive species. It compares two cases: the invasion process of Dreissena polymorpha in the Ebro River in Spain and the case of Hydrilla verticillata in Lake Izabal, Guatemala. Our results are structured according to impacts and to management options. The discussion focuses on the relevance of incorporating the different stakeholders' interests and values in the analysis and management of biological invasions. Although social analysis of stakeholders' positions is necessary in order to foster management actions, it also reveals conflicts on the relevant criteria and on the very definition of invasive species.