Jaime Palacio

Methylmercury Concentrations in Six Fish Species from Two Colombian Rivers

The objective of this study was to determine whether fish collected from the La Miel or Nechí Rivers (Colombia) differed in muscle methyl mercury (meHg) concentration. Two fish from six different species were collected from markets adjacent to each river. Overall, fish collected from the market adjacent to the Nechí River contained higher levels of meHg. This result however is being driven by very high meHg concentrations in four individual fish, three of which are Pimelodid, long-whiskered catfish. These catfish may represent ideal sentinel organism for the detection of meHg contamination in Colombian rivers.

Application of the micronucleus test and comet assay in Trachemys callirostris erythrocytes as a model for in situ genotoxic monitoring

Trachemys callirostris is a turtle species endemic to northern South America. In northern Colombia it occurs in the middle and lower Magdalena River drainage and its principal tributaries (lower Cauca and San Jorge rivers) and in other minor drainages such as the lower Sinú River. In recent years, industrial, agricultural, and mining activities have altered natural habitats in Colombia where this species occurs, and many of the pollutants released there are known to induce genetic alterations in wildlife species. The micronucleus test and comet assay are two of the most widely used methods to characterize DNA damage induced by physical and chemical agents in wildlife species, but have not been employed previously for genotoxic evaluations in T. callirostris. The goal of this study was to optimize these genotoxic biomarkers for T. callirostris erythrocytes in order to establish levels of DNA damage in this species and thereby evaluate its potential as a sentinel species for monitoring genotoxic effects in freshwater environments in northern Colombia. Both genotoxic techniques were applied on peripheral blood erythrocytes from 20 captive-reared T. callirostris individuals as a negative control, as well as from samples obtained from 49 individuals collected in Magangué (Magdalena River drainage) and 24 individuals collected in Lorica (Sinú River drainage) in northern Colombia. Negative control individuals exhibited a baseline frequency of micronuclei of 0.78±0.58 and baseline values for comet tail length and tail moment of 3.34±0.24µm and 10.70±5.5, respectively. In contrast, samples from both field sites exhibited significantly greater evidence of genotoxic effects for both tests. The mean MN frequencies in the samples from Magangué and Lorica were 8.04±7.08 and 12.19±12.94, respectively. The mean tail length for samples from Magangué and Lorica were 5.78±3.18 and 15.46±7.39, respectively. Finally, the mean tail moment for samples from Magangué and Lorica were 23.59±18.22 and 297.94±242.18, respectively. The frequency of micronuclei in the samples was positively related to comet tail length and tail moment. Thus, this study showed that both genotoxicity biomarkers may be applied to T. callirostris erythrocytes as a sentinel organism for assessing the effects of environmental pollutants in freshwater ecosystems in northern South America.

Effects of a cyanobacterial bloom sample containing microcystin-LR on the ecophysiology of Daphnia similis

Cyanobacterial blooms can affect a wide range of aquatic organisms due to the presence of toxic compounds. However, no study so far has shown the effects of natural blooms samples on the physiological parameters related to the ecology of Daphnia. In this study we used a natural bloom sample obtained from a reservoir in Colombia to evaluate its effects on five parameters related to Daphnias feeding behavior, swimming movements and physiology: second antennae movement (swimming), mandible movement (feeding), thoracic appendages (feeding), postabdomen movement (rejection of food particles) and heart rate (physiology). The results revealed significant changes in all parameters evaluated at two different concentrations of aqueous extracts of the bloom: second antennae movements increased significantly and there were significant reductions in mandibular movements, thoracic movements and heart rate. Although postabdominal movements showed high variability with no distinctive pattern between control and treatments, the reduction in the other parameters (such as heart rate over time) could possibly reflect an intoxication by microcystins or a behavioral response (e.g., feeding inhibition).

NIVELES DE MERCURIO EN HUEVOS, EMBRIONES Y NEONATOS DE Trachemys callirostris (TESTUDINES, EMYDIDAE)

We quantified total mercury concentrations in eggshells, egg yolks, and embryos from 16 nests of the Colombian Slider (Trachemys callirostris). Nests were collected in different stages of development, but estimated time of incubation in natural substrates was not correlated with mercury levels in the eggs, suggesting that mercury was not absorbed from the substrate, but more likely passed on to the embryos during folliculogenesis by the reproductive females who had bioaccumulated the mercury from environmental sources. Mean mercury concentrations were higher in embryos than in eggshells or egg yolks, indicating that embryos also bioaccumulate mercury present in other egg tissues. Intra-clutch variation in egg yolk mercury concentrations was relatively high. Egg yolk mercury concentrations were not associated with any of the fitness proxies we quantified for the nests (hatching success rates, initial neonate sizes and first-month juvenile growth rates). After five months of captive rearing in a mercury-free laboratory environment, 86 % of the juveniles had eliminated the mercury from their tissues.

Unmixing Progradational Sediments in a Southwestern Caribbean Gulf through Late Holocene: Backwash of Low-Level Atmospheric Jets

ABSTRACT Rúa, A.; Liebezeit, G.; Molina, R., and Palacio, J., 2016. Unmixing progradational sediments in a southwestern Caribbean gulf through late Holocene: Backwash of low-level atmospheric jets. In the last few years there has been considerable interest in the assessment of the role of tropical seas in driving paleoclimate. Despite this interest, little is known about the evolution of progradational sediments near the Panama Isthmus during the late Holocene. This paper shows the dispersion assessment of fluvial sediments into a gulf from the southwestern Caribbean on a decadal-centennial scale as recorded in three sediment cores spanning between 300 and 960 ± 35 calibrated YBP. According to end-member modeling of size classes, sediments largely comprised clay, clayey fine silt, and silty mud that flocculated by differential settling. Coarsened facies were consistent with enhanced fluvial discharge owing to increased precipitation in the circum-Caribbean. Remarkably, decreased fluvial discharge into the gulf due to aridity in the Caribbean was modulated by oceanic moisture conveyed by the low-level atmospheric jets of Panama and CHOCO. Fluvial sediments may surely fail to contribute to shoreline stability because of muddy hinterland lithology.

Effects of environmental factors on reproductive seasonality of Magdalena River basin fish: need for answers in the ecophysiology

Magdalena River basin is the core of development and economy of Colombia, with about 80% o f the countrys population (32 million) depending on it. This basin is drained by the Magdalena River and 3 main tributary rivers: Cauca, Sogamoso, and San Jorge, covering an area of 257 438 km (nearly a quarter ofColombias territory) (GALVIS & MoncA 2007). According to its geomorphologic features, this basin has been divided in 3 main sectors: Upper, Middle, and Lower. Flood plain areas appear in Middle basin and grow in the Lower. The number o f fish species reported for this basin i s 167, some migratory and important for artisanal fisheries. Although fishery captures were nearly 80 000 tons in the 1970s, only one-fifth that amount is produced now (GALVIS & MoncA 2007). Studies on reproductive biology ofMagdalena River basin fishes are crucial for fisheries management and environmental protection programs. Based on some information on environmental factors and fish reproduction from different places in Magdalena River, we list some possible physiological pathways induced by environmental cues and recommend some experimental approaches that would help clarify such relationships.