William D. Heyman

Automated Derivation of Bathymetric Information from Multi-Spectral Satellite Imagery Using a Non-Linear Inversion Model

Most previous studies utilized a log-linear regression model to invert multi-spectral images into bathymetric data. Based on the Levenberg-Marquardt optimization algorithm, we developed an automated method for calibrating the parameters for a non-linear inversion model. Our method has been successfully applied to an IKONOS multispectral image. We compared depth data derived from our model to those estimated using a conventional log-linear inversion model. Bathymetric data derived from the non-linear inversion model are slightly more accurate and stable, particularly for deeper benthic habitats, than those derived from a conventional log-linear model although their overall performances are very similar.

Introduction to the Special Issue: Marine and Coastal GIS for Geomorphology, Habitat Mapping, and Marine Reserves

This sixth special issue on Marine and Coastal Geographic Information Systems (M&CGIS) is the first to be based on an organized series of presentations at a conference, the 2008 Association of American Geographers (AAG) Annual Meeting in Boston, Massachusetts, USA. The papers were selected and peer reviewed for publication in this special issue under the theme “Marine Geomorphology as a Determinant for Essential Life Habitat: An Ecosystem Management Approach to Planning for Marine Reserve Networks” (see presentations and resources online at http://marinecoastalgis.net/aag08). The sessions were cosponsored by the Coastal and Marine, Geographic Information Science and Systems, and Biogeography specialty groups of the AAG. The unifying goal of these sessions was to examine critically the growing body of data suggesting that the underlying geology and geomorphology of marine environments dictate the location of critical life habitat for a variety marine species. For example, it is becoming clearer that spawning aggregations of many species of commercially important reef fishes commonly occur at the windward edge of reef promontories that jut into deep water (e.g., Heyman et al. 2007; Heyman et al. 2005). As another example, seamounts serve as attractors for pelagic fishes and as stepping stones for transoceanic species dispersal (e.g., de Forges et al. 2000; Stocks et al. 2004). The broad implications of these findings suggest that geomorphology might be used as a proxy for (or at least help to identify) critical life habitat for marine species and thus serve to advance

Hydrometeorology and Variability of Water Discharge and Sediment Load in the Inner Gulf of Honduras, Western Caribbean

The hydrological and meteorological characteristics of the watersheds of the inner Gulf of Honduras in the western Caribbean, including runoff, sediment load and yield, and the effects of the El Nino-La Nina cycle, are examined using available data. The inner Gulf of Honduras, bordered by the second-longest coral reef complex in the world, the MesoAmerican Barrier Reef, receives runoff from the watersheds of 12 rivers with a total simulated annual discharge of 1232 m 3 s 21. Expanding agricultural and industrial activities contribute to the influx of sediments, nutrients, and pollutants from these rivers, leading to increased threats to the health of the reef ecosystem. The watersheds of the Moho, Sarstun, and Polochic-Dulce Rivers receive more than 4000 mm of rainfall annually and are major sources of discharge and sediment load, along with the Motagua and Ulua, farther to the east. The drainage basins are characterized by runoff ratios of 0.30-0.55 and simulated sediment yields as high as 869 t km22 yr 21. The results from two different sediment load/yield models agree to within 62.3% at the 95% confidence level. Sediment load estimates increase by as much as 5 times on model comparisons of present land use to increased land use. Time series of precipitation for the inner Gulf of Honduras exhibit bimodal distribution with maxima in May-June and in September-October. Analysis of long-term climatic data reveals only a weak but measurable correlation with El Nino-La Nina. The Southern Oscillation index explains on average 7%-15% of the precipitation and temperature variability for the inner Gulf of Honduras.

Low-Cost Bathymetric Mapping for Tropical Marine Conservation—A Focus on Reef Fish Spawning Aggregation Sites

Marine conservation scientists and managers working in the tropics need bathymetric data, yet there exists no relatively simple and inexpensive system to derive them. We designed a system to produce bathymetric maps in 0–1,000 m water depth in less time, with less cost, and with less effort than any other system available. The system uses Landsat TM imagery to guide the collection and visualization of depth soundings obtained with a commercially available fish finder/GPS on a small boat. ArcGIS is used for interpolation and data display. The system was used to map two reef fish spawning aggregation sites in Belize and may be useful for shelf-edge mapping in other tropical locations.

Geomorphometric Patterns of Nassau Grouper (Epinephelus striatus) Spawning Aggregation Sites in the Cayman Islands

Reef fish spawning aggregation sites are essential life habitats vulnerable to exploitation by fishermen, yet no quantitative comparisons of sites exist to understand their geomorphologic patterns. The objective of this study was to evaluate the geospatial aspects of known Nassau grouper spawning aggregation sites in the Cayman Islands. The results illustrate that the five known Nassau grouper spawning aggregation sites are located at convex-shaped reefs within 1 km of reef promontory tips. Further, all sites are found in 25–45 m depth, less than 50 m from shelf edges. Finally, they have been documented as multi-species spawning aggregation sites.

Geographically Adaptive Inversion Model for Improving Bathymetric Retrieval From Satellite Multispectral Imagery

Optical remote sensing imagery offers a cost-effective alternative to echo sounding and bathymetric light detection and ranging surveys for deriving high density bottom depth estimates for coastal and inland water bodies. The common practice of previous studies has been to calibrate a single global bathymetric inversion model for an entire image scene. The performance of conventional global models is limited when the bottom type and water quality vary spatially within the scene. To address the inadequacy of the conventional global models, this paper presents a geographically adaptive inversion model to better estimate bottom depth. Although the general mathematical form of the geographically adaptive model is the same, model parameters are optimally determined within a geographical region or a local area, in contrast to the entire scene in the global inversion model. By using high-resolution IKONOS and moderate-resolution Landsat satellite images, we demonstrated that regionally and locally calibrated inversion models can effectively address the problems introduced by spatial heterogeneity in water quality and bottom type, and provide significantly improved bathymetric estimates for more complex coastal waters.

Elements for Building a Participatory, Ecosystem-Based Marine Reserve Network

This article offers a case study of the process involved in the development of a national network of marine reserves to protect multispecies reef fish spawning aggregation sites. There are two guiding principles that engendered success for this unprecedented conservation event. First was the broad participation of a diverse group of stakeholders, particularly the local fishermen providing their traditional ecological knowledge (TEK). The second involved the search for patterns in geomorphology and its association to the biology of exploited species. Using diverse and patchy sets of data including published peer-reviewed papers, gray literature reports from Belize and other Caribbean nations, remotely sensed images, coarse bathymetric maps, new bathymetric data collected with a single-beam sonar, and reports of fishermen from various parts of the country, we developed a conceptual understanding summarized by the multispecies promontory hypothesis, which suggests a common geomorphology of spawning sites for most large and commercially important reef fish species. An explicit test of the hypothesis is presently underway but is not the only focus of this article. This article also addresses the participatory process of geographic discovery and the role of the process in building consensus around a functional biophysical hypothesis, its test, and the resulting conservation action. A holistic, eclectic, inclusive geographic approach is offered as a successful example.

Marine Geomorphology in the Design of Marine Reserve Networks

Marine environments, key life-support systems for the earth, are under severe threat. Issues associated with managing these common property resources are complex and interrelated. Networks of marine reserves can be valuable for mitigating threats to marine systems, yet the successful design and implementation of such networks has been limited. Efficient ways to conserve marine environments are urgently needed. This Focus Section of The Professional Geographer explores the development of marine reserve networks based on geomorphology, fish biology, ecological connectivity, and appropriate governance. The articles in this Focus Section offer examples of the following: (1) distinctive reef geomorphology dictating the spawning locations of reef fishes, which in turn serve as critical source sites for the replenishment of distant reefs by means of larval transport; (2) an example of a simplified oceanographic model that predicts larval transport from fish breeding sites to important nursery areas; and (3) a case study of the development of a marine reserve network that illustrates key elements of a successful strategy. In sum, this Focus Section offers case studies that show the value of marine geomorphology, oceanographic connectivity, and stakeholder involvement as key elements of multidisciplinary geographic studies applied to the design of marine reserve networks. Geographers can further contribute to the conservation and management of coastal and marine ecosystems in many ways that involve subdisciplines of remote sensing and geographic information systems, political and economic geography, political ecology, and ethnography.

South-South exchanges enhance resource management and biodiversity conservation at various scales

International conservation organisations have invested considerable resources in fostering biodiversity conservation programs in the humid tropics, the most biologically diverse areas on earth. Recent approaches to conservation have centered on integrated conservation and development projects and participatory resource management programs, co-managed between governments and local communities. But these programs have had only mixed success and often suffer from insufficient quantity or quality of participation by local communities. We pose that participatory resource management is more likely to succeed when community members, 1) gain a global perspective on how their social, economic and environmental conditions compare with peer communities in other similar areas of the world, and thus better understand issues of relative scarcity and the benefits of sustainable resource management, and 2) engage as decision-makers at every stage of the conservation process up to reflective program evaluation. This paper examines the role of South-South exchanges as a tool to achieve these intermediate goals that ultimately foster more effective and participatory conservation and support sustainable local livelihoods. The data are extracted from the initiatives of the authors in two different environments- marine and coastal communities in Central America and the Caribbean, and lowland rainforest communities in the western Amazon of South America. We conclude that the exchanges are effective ways to build stakeholder comprehension about, and meaningful engagement in, resource management. South-South exchanges may also help build multi-local coalitions from various remote areas that together support biodiversity conservation at regional and global scales.

Geomorphology of Reef Fish Spawning Aggregations in Belize and the Cayman Islands (Caribbean)

Publisher Summary Caye Glory and Gladden Spit in Belize, and Grand Cayman East (GCE) and Little Cayman West (LCW) in the Cayman Islands, have a common geomorphologic signature and all harbor important breeding grounds for commercially important reef fishes. Most commercially important reef fishes, including many species of grouper and snapper, travel relatively long distances over the course of days or weeks to aggregate and spawn at very specific times and in very specific places. Locations of known sites were compiled using published literature and new field surveys and indicate commonality in the underlying geomorphology and species seasonality of reef fish spawning aggregation (FSA) sites throughout the wider Caribbean. Commercially important reef fish such as grouper and snapper use specific geomorphologic locations as spawning grounds throughout the wider Caribbean. In the Cayman Islands and Belize, fish choose shelf-edge reef promontories for spawning, and share these areas with other species. These multispecies spawning aggregation sites are generally located near the inflection points of convex-shaped reefs, in 20–40 m water depth, adjacent to sharp shelf edges where water depth drops to several hundred meters. Reef geomorphology may be the key determinant for the selection of reef fish breeding habitat. This chapter presents the three-dimensional structure of four representative spawning aggregation sites in the Cayman Islands and Belize.