Abstract The theory of island biogeography was tested in Nicaraguan volcanic crater lakes, colonized by fish from the older and larger source Nicaraguan Great Lakes. Spearman correlations of ranked molecular phylogenetic diversity in the Midas cichlid species complex ( Amphilophus cf. citrinellus ) were significant ( p ≤ 0.05) or marginally significant (0.05 < p ≤ 0.10) with diversity with crater lake age in three of four data sets tested. Correlations were noted with deepwater area, the product of littoral area and age, and with the product of horizontal and vertical barriers between the crater lakes and the nearest source lakes divided by the product of littoral area and age. By treating the Midas cichlid species complex as a single taxon, ranked fish taxon richness in each lake correlated significantly with lake age, littoral area, and with the product of age and littoral area. These results support the concept that littoral area and lake age may be factors in the colonization of volcanic crater lakes from the source lakes, and the amount of deep water in a lake as well as lake age may be important factors in speciation in the Midas cichlid species complex. Seven species from the crater lakes have been classified as Critically Endangered by the IUCN.

Abstract It is a great importance of finding the cost-effective strategy of treating chromite ore processing residue (COPR). Cr(Ⅵ), presented in aqueous media, could easily be reduced, adsorption and removed from water body through a proper treatment, but Cr(Ⅵ), incorporated in COPR, could not, due to its characteristic inherent to COPR. In general, the reduction and adsorption of Cr(Ⅵ) could take place at a low pH, the COPR, however, has a high acid neutralizing capacity, so that a great deal of the inorganic acid would be required to maintain its pH at low value. In this work, a series of treatment trials, comprised of the production of chromate from COPR by leaching process, the subsequent detoxification and in-situ stabilisation of post-leached COPR (plCOPR) were conducted. After column extracting process using the seawater, Cr(Ⅵ)-containing leachate of 600~800 mg/L is led to the ion exchange columns, charged with the anion exchange resin, to adsorb the Cr(Ⅵ) until the effluent contains Cr(Ⅵ) of 5 mg/L. The Cr(Ⅵ) loaded ion exchange column was eluted by NaOH solution and the maximum concentration of Cr(Ⅵ) in the elution was 43.1 g/L. Afterward, plCOPR was mixed with sodium sulfide and iron sulfide+lime as a reductant and a stabiliser, respectively, and the mixture was discharged directly from the mixer and piled on a certain area. After 360 d of curing, Cr(VI) concentration in the leachate from the toxicity characteristic leaching procedure (TCLP) was arrived at 1.2 mg/L, below the regulatory limit disposal standard (HJ/T 301-2007, 3 mg/L).