Sediment and soil organic matter source assessment as revealed by the molecular distribution and carbon isotopic composition of n-alkanes

The assessment of organic matter (OM) sources in sediments and soils is a key to better understand the biogeochemical cycling of carbon in aquatic environments. While traditional molecular marker-based methods have provided such information for typical two end member (allochthonous/terrestrial vs. autochthonous/microbial)-dominated systems, more detailed, biomass-specific assessments are needed for ecosystems with complex OM inputs such as tropical and sub-tropical wetlands and estuaries where aquatic macrophytes and macroalgae may play an important role as OM sources. The aim of this study was to assess the utility of a combined approach using compound specific stable carbon isotope analysis and an n-alkane based proxy (Paq) to differentiate submerged and emergent/terrestrial vegetation OM inputs to soils/sediments from a sub-tropical wetland and estuarine system, the Florida Coastal Everglades. Results show that Paq values (0.13–0.51) for the emergent/terrestrial plants were generally lower than those for freshwater/marine submerged vegetation (0.45–1.00) and that compound specific δ13C values for the n-alkanes (C23 to C31) were distinctively different for terrestrial/emergent and freshwater/marine submerged plants. While crossplots of the Paq and n-alkane stable isotope values for the C23n-alkane suggest that OM inputs are controlled by vegetation changes along the freshwater to marine transect, further resolution regarding OM input changes along this landscape was obtained through principal component analysis (PCA), successfully grouping the study sites according to the OM source strengths. The data show the potential for this n-alkane based multi-proxy approach as a means of assessing OM inputs to complex ecosystems.

Diel and seasonal variation in the use of a nearshore sandflat by a ray community in a near pristine system

Knowledge of movements and habitat use is necessary to assess a species’ ecological role and is especially important for mesopredators because they provide the link between upper and lower trophic levels. Using acoustic telemetry, we examined coarse-scale diel and seasonal movements of elasmobranch mesopredators on a shallow sandflat in Shark Bay, Western Australia. Giant shovelnose rays (Glaucostegus typus) and reticulate whiprays (Himantura uarnak) were most often detected in nearshore microhabitats and were regularly detected throughout the day and year, although reticulate whiprays tended to frequent the monitored array over longer periods. Pink whiprays (H. fai) and cowtail stingrays (Pastinachus atrus) were also detected throughout the day, but were far less frequently detected. Overall, there was no apparent spatial or temporal partitioning of the sandflats, but residency to the area varied between species. In addition, ray presence throughout the year suggests that previously observed differences in seasonal abundance are likely because of seasonal changes in habitat use rather than large-scale migrations. Continuous use of the sandflats and limited movements within this ray community suggests that rays have the potential to be a structuring force on this system and that focusing on nearshore habitats is important for managing subtropical ray populations.

Indirect and direct controls of macroinvertebrates and small fish by abiotic factors and trophic interactions in the Florida Everglades

1. The roles of nutrients, disturbance and predation in regulating consumer densities have long been of interest, but their indirect effects have rarely been quantified in wetland ecosystems. The Florida Everglades contains gradients of hydrological disturbance (marsh drying) and nutrient enrichment (phosphorus), often correlated with densities of macroinvertebrate infauna (macroinvertebrates inhabiting periphyton), small fish and larger invertebrates, such as snails, grass shrimp, insects and crayfish. However, most causal relationships have yet to be quantified. 2.  We sampled periphyton (content and community structure) and consumer (small omnivores, carnivores and herbivores, and infaunal macroinvertebrates inhabiting periphyton) density at 28 sites spanning a range of hydrological and nutrient conditions and compared our data to seven a priori structural equation models. 3.  The best model included bottom-up and top-down effects among trophic groups and supported top-down control of infauna by omnivores and predators that cascaded to periphyton biomass. The next best model included bottom-up paths only and allowed direct effects of periphyton on omnivore density. Both models suggested a positive relationship between small herbivores and small omnivores, indicating that predation was unable to limit herbivore numbers. Total effects of time following flooding were negative for all three consumer groups even when both preferred models suggested positive direct effects for some groups. Total effects of nutrient levels (phosphorus) were positive for consumers and generally larger than those of hydrological disturbance and were mediated by changes in periphyton content. 4.  Our findings provide quantitative support for indirect effects of nutrient enrichment on consumers, and the importance of both algal community structure and periphyton biomass to Everglades food webs. Evidence for top-down control of infauna by omnivores was noted, though without substantially greater support than a competing bottom-up-only model.

Silence by Stealth: Freedom of the Press and Polarization in Latin America

The weak democratic systems that followed decades of military dictatorships in Latin America coupled with the emergence of new authoritarian regimes of the left have had a significant impact on the relationships between the governments and the media. The new populist leaders have challenged the media that have generally reflected the perspectives of the traditional elites. This ideological clash has renewed direct and indirect censorship, curtailing freedom of expression and thus, freedom of the press. In this context, this paper discusses the mechanisms used by Latin American governments, particularly the new authoritarianism of the left, to silence dissident voices. Many of these mechanisms are legal, found in laws related to personal injury and defamation. Others have been of constitutional nature, invoking states of emergency or national security concerns. Some governments have used institutional means to close down newspapers and other sources of information. Current media conditions in Latin America show growing polarization. This has led to considerable levels of violence and intimidation against editors, journalists, and news crews in several countries. It is precisely this type of deterioration of fundamental rights that leads to questioning the strength and sustainability of Latin American democracies.

Law Enforcement Actions in Urban Spaces Governed by Violent Non-State Entities: Lessons from Latin America

In response to a crime epidemic afflicting Latin America since the early 1990s, several countries in the region have resorted to using heavy-force police or military units to physically retake territories de facto controlled by non-State criminal or insurgent groups. After a period of territory control, the heavy forces hand law enforcement functions in the retaken territories to regular police officers, with the hope that the territories and their populations will remain under the control of the state. To a varying degree, intensity, and consistency, Brazil, Colombia, Mexico, and Jamaica have adopted such policies since the mid-1990s. During such operations, governments need to pursue two interrelated objectives: to better establish the state’s physical presence and to realign the allegiance of the population in those areas toward the state and away from the non-State criminal entities. From the perspective of law enforcement, such operations entail several critical decisions and junctions, such as: Whether or not to announce the force insertion in advance. The decision trades off the element of surprise and the ability to capture key leaders of the criminal organizations against the ability to minimize civilian casualties and force levels. The latter, however, may allow criminals to go to ground and escape capture. Governments thus must decide whether they merely seek to displace criminal groups to other areas or maximize their decapitation capacity. Intelligence flows rarely come from the population. Often, rival criminal groups are the best source of intelligence. However, cooperation between the State and such groups that goes beyond using vetted intelligence provided by the groups, such as a State tolerance for militias, compromises the rule-of-law integrity of the State and ultimately can eviscerate even public safety gains. Sustaining security after initial clearing operations is at times even more challenging than conducting the initial operations. Although unlike the heavy forces, traditional police forces, especially if designed as community police, have the capacity to develop trust of the community and ultimately focus on crime prevention, developing such trust often takes a long time. To develop the community’s trust, regular police forces need to conduct frequent on-foot patrols with intensive nonthreatening interactions with the population and minimize the use of force. Moreover, sufficiently robust patrol units need to be placed in designated beats for substantial amount of time, often at least over a year. Establishing oversight mechanisms, including joint police-citizens’ boards, further facilities building trust in the police among the community. After disruption of the established criminal order, street crime often significantly rises and both the heavy-force and community-police units often struggle to contain it. The increase in street crime alienates the population of the retaken territory from the State. Thus developing a capacity to address street crime is critical. Moreover, the community police units tend to be vulnerable (especially initially) to efforts by displaced criminals to reoccupy the cleared territories. Losing a cleared territory back to criminal groups is extremely costly in terms of losing any established trust and being able to recover it. Rather than operating on a priori determined handover schedule, a careful assessment of the relative strength of regular police and criminal groups post-clearing operations is likely to be a better guide for timing the handover from heavy forces to regular police units. Cleared territories often experience not only a peace dividend, but also a peace deficit – in the rise new serious crime (in addition to street crime). Newly – valuable land and other previously-inaccessible resources can lead to land speculation and forced displacement; various other forms of new crime can also significantly rise. Community police forces often struggle to cope with such crime, especially as it is frequently linked to legal business. Such new crime often receives little to no attention in the design of the operations to retake territories from criminal groups. But without developing an effective response to such new crime, the public safety gains of the clearing operations can be altogether lost.

A Map Through Time – Virtual Historic Cities: New Ways of Exploring Digital Collections

Presentation made by Jamie Rogers and John Nemmers at the Society of Florida Archivists annual meeting in Tallahassee, Florida. Jamie Rogers presented the "Coral Gables - Virtual Historic City" project at Florida International University. John Nemmers presented the "Unearthing St. Augustine’s Colonial Heritage" project at the University of Florida

Stoichiometry, growth, and fecundity responses to nutrient enrichment by invertebrate grazers in sub-tropical turtle grass (Thalassia testudinum) meadows

Although the effectiveness of herbivores in mitigating the effects of nutrient enrichment is well documented, few studies have examined the effects of nutrient enrichment on components of consumer fitness. Enclosures were deployed in shallow turtle grass (Thalassia testudinum) beds in Florida Bay, Florida in fall 2003, spring 2004, and fall 2004 to measure the effects of nitrogen and phosphorous enrichment on the growth, fecundity, and stoichiometry of three invertebrate epiphyte grazers commonly associated with T. testudinum. The gastropod Turbo castanea exhibited significantly greater wet weight gain and lower C:P and N:P in enriched than in ambient treatments. Although nutrient enrichment did not have any significant effects on the growth of caridean shrimp (treatment consisted of several different caridean shrimp species), their C:N was significantly lower in enriched treatments. The final size and stoichiometry of the hermit crab Paguristes tortugae was not significantly affected by nutrient enrichment, nor did nutrient enrichment significantly affect the fecundity of P. tortugae, the only grazer in which gravid individuals or egg masses were present. Our study demonstrated that nutrient enrichment of primary producers can positively affect the growth of marine invertebrate grazers and alter their stoichiometry; however, these effects were species-specific and may be dependent upon the life stage, specific diets, and/or compensatory feeding habits of the grazers.

Frugivory and Seed Dispersal by Crocodilians: An Overlooked Form of Saurochory?

Saurochory (seed dispersal by reptiles) among crocodilians has largely been ignored, probably because these reptiles are generally assumed to be obligate carnivores incapable of digesting vegetable proteins and polysaccharides. Herein we review the literature on crocodilian diet, foraging ecology, digestive physiology and movement patterns, and provide additional empirical data from recent dietary studies of Alligator mississippiensis. We found evidence of frugivory in 13 of 18 (72.2%) species for which dietary information was available, indicating this behavior is widespread among the Crocodylia. Thirty-four families and 46 genera of plants were consumed by crocodilians. Fruit types consumed by crocodilians varied widely; over half (52.1%) were fleshy fruits. Some fruits are consumed as gastroliths or ingested incidental to prey capture; however, there is little doubt that on occasion, fruit is deliberately consumed, often in large quantities. Sensory cues involved in crocodilian frugivory are poorly understood, although airborne and waterborne cues as well as surface disturbances seem important. Crocodilians likely accrue nutritional benefits from frugivory and there are no a priori reasons to assume otherwise. Ingested seeds are regurgitated, retained in the stomach for indefinite and often lengthy periods, or passed through the digestive tract and excreted in feces. Chemical and mechanical scarification of seeds probably occurs in the stomach, but what effects these processes have on seed viability remain unknown. Because crocodilians have large territories and undertake lengthy movements, seeds are likely transported well beyond the parent plant before being voided. Little is known about the ultimate fate of seeds ingested by crocodilians; however, deposition sites could prove suitable for seed germination. Although there is no evidence for a crocodilian-specific dispersal syndrome similar to that described for other reptiles, our review strongly suggests that crocodilians function as effective agents of seed dispersal. Crocodilian saurochory offers a fertile ground for future research.