The study was conducted in the semi-enclosed waters of Lamong Bay, Surabaya, and Benoa Bay, Bali, Indonesia in March 2017. Sediment samples were taken using a simple core made from PVC pipe, 2 inches diameter. Several core samples were taken in each study site. For further analysis, one of the longest and most intact core samples without litter inserts was selected from each site. The core samples were stored in the freezer for further analysis. Several series of sub samples on 5 cm intervals of core sediment were used to measure chronological absolute age, the foraminiferal abundance and sedimentation rate. The chronological of absolute age of the sediment deposition were measured based on the activity of Pb210 isotope (in the half-life time of 22.3 years) at the National Nuclear Energy Agency. These methods were useful in measuring 150-200 years of chronological age in accommodating sediments, i.e., sediments with minor diffraction levels. Diffraction in sediments can occur due to contamination that disrupts the content of the Pb210 isotope or as a result of geological processes in the substratum region. Foraminifera and sediments identification were carried out at the Laboratory of Research Center for Oceanography– Indonesian Institute of Sciences. Identification and calculation of foraminiferal abundance were using Nikon Labophot’s low power microscope.
Author(s) Details:
Rositasari
Research Center for Oceanography-National Research and Innovation Agency Jl, Pasir Putih I, Ancol Timur, Jakarta Utara, 1440, Indonesia.
Recent global research developments in Chronological Analysis of Sediment Deposition in Lamong Bay and Benoa Bay Using Foraminiferal Proxies
1. A Retrospective Study of Semi-Enclosed Bays Based on Short Core Samples in Surabaya and Bali, Indonesia:
- This study aimed to determine past ecological changes based on paleoenvironmental analysis in two bays with very different environmental development characteristics: Lamong Bay in Surabaya and Benoa Bay in Bali.
- Sampling: Conducted in March 2017, the study included the analysis of absolute age and sedimentation rate using the Pb-210 isotope and recent foraminifera indexing from short core samples.
- Foraminifera Proxy: Benthic foraminifera were used as a proxy to reveal the ecological development of these semi-enclosed bays over time periods.
- Ecological Changes:
- Lamong Bay: Over the past 87 years, Lamong Bay has undergone significant ecological changes. It transitioned from an aquatic environment strongly influenced by the open sea (supporting benthic life) to shallow oligotrophic waters that cannot support benthic life.
- Benoa Bay: In contrast, Benoa Bay has remained shallow for the past 50 years and continues to support benthic life without the threat of hypoxia due to eutrophication.
- The study provides useful baseline information for stakeholders in preparing disaster mitigation plans for these coastal areas [1].
References
- Rositasari, R., & Purbonegoro, T. (2021). A Retrospective Study of Semi-Enclosed Bays Based on Short Core Samples in Surabaya and Bali, Indonesia. IOP Conference Series: Earth and Environmental Science, 789, 012017. Read the full article
