Environmental DNA Biomonitoring Reveals Seasonal Patterns in Coral Reef Fish Community Structure

Coral reef fish populations are declining due to multiple factors including habitat destruction, overfishing, and climate change. While these can include seasonal impact, seasonal changes can also be a confounding factor, so that seasonal monitoring is essential for detecting true temporal changes in fish community abundance and composition. However, seasonal monitoring is rarely implemented. The aim of this study was to detect the seasonal patterns of coral reef fish community structure around Tidung Kecil Island, Indonesia, using eDNA metabarcoding (eDNA) and underwater visual census (UVC). The UVC identified 32 species belonging to 10 families in the rainy season and 29 species belonging to 7 families in the dry seasons. The eDNA metabarcoding identified 209 species belonging to 56 families and 27 species belonging to 17 families in the rainy and dry seasons, respectively. Based on eDNA metabarcoding data, coral reef fish abundance and community composition differed significantly between seasons (Mann Whitney, p<0.01), while the UVC method did not detect these seasonal differences (Mann Whitney, p>0.05). UVC and eDNA data both showed a predominance of omnivorous fishes in the rainy season and carnivorous fishes in the dry season. Ecological indices did not differ significantly between seasons for either method, although the species making the highest contributions to the similarity (SIMPER) analysis differed between methods. Overall, this study confirms the premise that eDNA metabarcoding can be an effective tool for monitoring seasonal variation in coral reef fish communities.

A Case Study - Life Extension of Offshore Bridge Bearings

Structural bearings of 47 offshore platform-link bridges with average age of 40 years were inspected and recommended for replacements due to their poor condition. Replacement of bridge bearings involves major risk and production interruptions given the structural modifications, and critical piping and E&I disconnections required for safe jacking-lifting activities required during the process. This paper presents the approach adopted to assure the integrity of the bridges and extend their lives without the need to replace the bearings. The approach employed failure mode and effect analysis to identifying and narrowing down areas that need focused efforts while tackling the problem. Scenario based structural assessments were carried out to examine the impact of the level of movement-allowing bearings functionality on the integrity of the bridge and its supporting structures; identify critical locations to be targeted during focused inspections; and establish envelopes for monitoring thermal expansion and contraction of the bridges. Guidelines were developed and implemented for integrated inspection-maintenance and repair campaign, which aimed to tackle corrosion issues and to install movement-monitoring indicators. Indicator seasonal monitoring is employed to establish the functionality of bearings on the long-term. The what-if structural assessments revealed that even in the worst-case scenario (in which the bearing are completely jammed) the option of local strengthening of the bridge and its supporting elements is more attractive than bearing replacement. The integrated inspection-maintenance and repair campaigns revealed that excessive corrosion levels observed from historic visual inspections on external non-critical bearing components (e.g: guide plates, angles, etc.) is not indicative of the condition of the internal load-bearing components (pedestals) which experienced much lower corrosion levels. The seasonal monitoring of bridge movements revealed that the 40+ years old Teflon pads are still functional and allow the bridges expansion and contraction. The developed holistic approach enabled demonstration of the fitness for service of the bearings, and provided means for assuring their long-term performance through monitoring. The results assured safety, integrity and delivered significant cost savings through aversion brownfield modifications, and production loss associated with bridge jacking and bearing replacement operations.

Groundwater quality assessment of protected aquatic eco-systems in cross-border areas of Serbia and Croatia

Research results define basis for specific monitoring programs of gro-undwater quality in wetland eco-systems in Serbia and Croatia. The main pur-pose of the research was to determine the impact of nonpoint diffuse source pollution on the groundwater quality, as well as seasonal variations on the con-centration levels of selected physico-chemical parameters. Statistical analyses, PCA, HCA, ANOVA and t-test, encompass 18 monitored parameters in ground-water. Statistical data indicated that protected area in Serbia has a significantly higher load of pollution from agricultural activities compared to Wetlands Tompojevci. The highest load in groundwater was detected from total nitrogen, ammonia and nitrogen anions, indicating contamination of groundwater by nitrogen-based fertilizers. The results obtained within the two-year seasonal monitoring program, from 2018 to 2020, are highly essential for achieving a comprehensive database that could be used as platform for high-quality groundwater management in selected protected areas with the aim of minimizing environmental pollution.

Seasonal monitoring of Cryptosporidium species and genetic diversity in neonatal dairy calves on two large-scale farms in Xinjiang, China

Background: Neonatal dairy calves infected with Cryptosporidium can possess a significant source of zoonotic infections and disease. To assess seasonal variations in the prevalence and genetic diversity of Cryptosporidium in neonatal dairy calves, 380 fecal samples from neonatal dairy calves on two large-scale farms in Xinjiang (Alaer and Wensu) were screened for the Cryptosporidium small subunit (SSU) rRNA gene. Results: The overall prevalence of Cryptosporidium was 48.7% (185/380): 48.6% (108/222) in Alaer and 48.7% (77/158) in Wensu. Cryptosporidium was most frequent in summer (56.8%, 54/95), followed by spring (50.0%, 44/88), winter (46.8%, 44/94), and autumn (41.7%, 43/103) (P > 0.05). Cryptosporidium was significantly more prevalent in calves with diarrhea (72.4%, 113/156) than in those without (32.1%, 72/224) (P < 0.01). Based on a restriction fragment length polymorphism (RFLP) analysis, C. parvum (n = 173), C. bovis (n = 7), C. ryanae (n = 3), and co-infections of the three species (n = 2) were identified. Most (172/175) C. parvum samples were successfully sequenced at the 60-kDa glycoprotein gene (gp60), revealing two zoonotic subtypes: IIdA14G1 (n = 94) and IIdA15G1 (n = 7) in Alaer and IIdA15G1 (n = 71) in Wensu.Conclusions: These results showed that neonatal dairy calves were commonly infected with Cryptosporidium throughout the year, and there was a significant association between the occurrence of diarrhea and Cryptosporidium infection. Presence of IIdA14G1 and IIdA15G1 indicated neonatal dairy calves may be a source of zoonotic C. parvum subtypes.