Littoral decapods of Socorro Island, Revillagigedo Archipelago, Mexico

Decapod community inhabiting the rocky littoral of eight bays from Socorro island, Revillagigedo Archipelago, was studied during March 1992. Samples were collected from one-square meter plots placed following transects drawn perpendicularly to the shoreline along the intertidal zone. Species richness and abundance were determined in each bay, as well as the similarity between bays using Morisita's index. Organisms collected belong to six families, 20 genera and 26 species of the Brachyura and Anomura infraorders. Xanthidae was the family with the highest number of species, and the highest species richness was recorded at the V. Lozano bay. Pachygrapsus transversus, Xanthodius cooksoni and Calcinus explorator were the most abundant species in nearly all localities. Dendrogram obtained define two groups of bays at a similarity level above 0.67, given the similarity in the crab's species richness and their abundance between bays in the island.

Littoral decapods of Socorro Island, Revillagigedo Archipelago, Mexico.

Decapod community inhabiting the rocky littoral of eight bays from Socorro island, Revillagigedo Archipelago, was studied during March 1992. Samples were collected from one-square meter plots placed following transects drawn perpendicularly to the shoreline along the intertidal zone. Species richness and abundance were determined in each bay, as well as the similarity between bays using Morisita's index. Organisms collected belong to six families, 20 genera and 26 species of the Brachyura and Anomura infraorders. Xanthidae was the family with the highest number of species, and the highest species richness was recorded at the V. Lozano bay. Pachygrapsus transversus, Xanthodius cooksoni and Calcinus explorator were the most abundant species in nearly all localities. Dendrogram obtained define two groups of bays at a similarity level above 0.67, given the similarity in the crab's species richness and their abundance between bays in the island.

[Abundance and diversity of littoral invertebrates in the Socorro Island, Revillagigedo Archipelago, Mexico]. / Abundancia y diversidad de los invertebrados litorales de isla Socorro, Archipiélago Revillagigedo, México.

Composition, abundance, diversity and distribution of the littoral benthic invertebrates of Socorro Island with transects (parallel to the coast and with 1 m2 quadrats) were analyzed. During the spring of 1991 and 1992 samples were taken from the upper and middle levels of the intertidal zone in Vargas Lozano, Braithwaite, Blanca SW, Blanca NE, Binners, Grayson, Academia and Norte bays. The 161 species found belong to Porifera, Cnidaria, Platyhelmintha, Nemertina, Sipunculida, Annelida, Mollusca, Anthropoda and Echinodermata. Crustaceans and mollusks were the richest groups in both years, as in other rocky shores. Highest total density was found in Blanca NE bay in both samplings, with 281 orgs./m2 in the first and 172 orgs./m2 in the second. Most frequently found species were Isognomon janus (Mollusca, Pelecypoda), Littorina pullata (Mollusca, Gastropoda), Hipponix panamensis (Mollusca, Gastropoda), Pachygrapsus transversus (Crustacea, Grapsoidea) and Turbo funiculosus (Mollusca, Gastropoda). Because of the complexity of the habitat structure, Vargas Lozano was the bay with the highest specific richness (83 species), greatest diversity (4.7 bits/individual) and lowest dominance (0.065). Most species were classified as accidentals with the Dajoz's frequency classification, while the dominant species were accessories and only I. janus, in the spring 1991, was a constant species. Two kinds of bays were distinguished: those with some dominant species (density) and those in which there was no evident dominance by a particular species. Consequently, the diversity and evenness values were set apart: homogeneous communities (Vargas Lozano and Binners) and heterogeneous communities (Grayson bay and others), characterized by intermediate evenness values. The Jaccard similarity index identified two regions: one formed by bays found mainly in the southwest part of the island (Binners, Vargas Lozano, Braithwaite, Grayson and Blanca SW) and the other found in the northern region that included Blanca NE, Academia and Norte; however, Blanca NE had the most diverse species composition because of its physiographic particularities and because the sediment retained by the filamentous algae on the flat stones allow many species to settle down. Isognomon janus, Mitrella baccata (Mollusca, Gastropoda), P. transversus and Xanthodius cooksoni (Crustacea, Xanthoidea) were the most common species in all bays in both expeditions. The dominance-diversity relationship, the high specific richness and the low dominance of coastal invertebrates from the different bays, are indicative that the communities in Socorro Island are little disturbed; their specific richness are similar to those of coral reefs.

Abundancia y diversidad de los invertebrados litorales de isla Socorro, ArchipiÚlago Revillagigedo, México / Abundance and diversity of littoral invertebrates in the Socorro Island, Revillagigedo Archipelago, Mexico

Composition, abundance, diversity and distribution of the littoral benthic invertebrates of Socorro Island with transects (parallel to the coast and with 1 m2 quadrats) were analyzed. During the spring of 1991 and 1992 samples were taken from the upper and middle levels of the intertidal zone in Vargas Lozano, Braithwaite, Blanca SW, Blanca NE, Binners, Grayson, Academia and Norte bays. The 161 species found belong to Porifera, Cnidaria, Platyhelmintha, Nemertina, Sipunculida, Annelida, Mollusca, Anthropoda and Echinodermata. Crustaceans and mollusks were the richest groups in both years, as in other rocky shores. Highest total density was found in Blanca NE bay in both samplings, with 281 orgs./m2 in the first and 172 orgs./m2 in the second. Most frequently found species were Isognomon janus (Mollusca, Pelecypoda), Littorina pullata (Mollusca, Gastropoda), Hipponix panamensis (Mollusca, Gastropoda), Pachygrapsus transversus (Crustacea, Grapsoidea) and Turbo funiculosus (Mollusca, Gastropoda). Because of the complexity of the habitat structure, Vargas Lozano was the bay with the highest specific richness (83 species), greatest diversity (4.7 bits/individual) and lowest dominance (0.065). Most species were classified as accidentals with the Dajoz's frequency classification, while the dominant species were accessories and only I. janus, in the spring 1991, was a constant species. Two kinds of bays were distinguished: those with some dominant species (density) and those in which there was no evident dominance by a particular species. Consequently, the diversity and evenness values were set apart: homogeneous communities (Vargas Lozano and Binners) and heterogeneous communities (Grayson bay and others), characterized by intermediate evenness values. The Jaccard similarity index identified two regions: one formed by bays found mainly in the southwest part of the island (Binners, Vargas Lozano, Braithwaite, Grayson and Blanca SW) and the other found in the northern region that included Blanca NE, Academia and Norte; however, Blanca NE had the most diverse species composition because of its physiographic particularities and because the sediment retained by the filamentous algae on the flat stones allow many species to settle down. Isognomon janus, Mitrella baccata (Mollusca, Gastropoda), P. transversus and Xanthodius cooksoni (Crustacea, Xanthoidea) were the most common species in all bays in both expeditions. The dominance-diversity relationship, the high s

Solid waste characterisation study in the Guadalajara Metropolitan Zone, Mexico.

The key findings of a solid waste characterisation study conducted at the Guadalajara Metropolitan Zone, Mexico, are reported. Objectives of the study were to estimate the daily generation rate of household (HSW) and municipal solid waste (MSW), characterise and compare their composition by type of material, determine the proportion that HSW contributes to MSW, explore changes in MSW composition through time after final disposal, and estimate the types and amount of MSW that are sorted out for recycling at final disposal sites. HSW generated during seven days by a sample of 300 households chosen through a two-stage stratified sampling design was collected, weighed and classified. MSW entering the four local disposal sites was recorded for 12 weeks, and materials' sorting was quantified. MSW samples taken by excavating trenches in two final disposal sites were also characterised. The average per capita daily HSW generation rate was 508 g. HSW mainly consisted of putrescible waste (53%), paper (10%) and plastic (9%). The average daily generation rate of MSW was 3119.2 metric tonnes. HSW represented 55.9% of MSW, and the main difference between HSW and MSW was a lower proportion of organic materials (53% vs. 16.5%, respectively). The major changes in MSW composition through time after final disposal, were the result of the quick decomposition of putrescible materials. Only 2.2% of total MSW generated in Guadalajara (mainly package waste) was sorted for recycling.