Ichnofabric analysis as a tool for characterization and differentiation between calcareous contourites and calciturbidites

ABSTRACT The Eocene–Miocene Cyprus paleoslope system records complex deep-marine sedimentation comprising background vertical settling of autochthonous pelagic–hemipelagic particles (chalks) which were punctuated by calcareous bottom currents (contourites) and gravity flows (calciturbidites). The Eocene Lefkara Formation at the Petra Tou Romiou beach section (Cyprus) shows the incidence of deep-marine bottom currents and distal turbiditic episodes in a context of pelagic–hemipelagic sedimentation. Trace-fossil analysis of this section, using an ichnofabric approach (i.e., ichnodiversity, Bioturbation Index, Bedding Plane Horizontal Index and crosscutting relationships), was conducted to precisely describe the paleoenvironmental conditions of this complex setting. Ichnofabric analysis allow the characterization and differentiation of sporadic turbiditic events that disrupted both pelagic–hemipelagic and contourite deposition. Calciturbidite intervals show ichnofabrics consisting of postdepositional U-shaped traces (i.e., Arenicolites isp., ?Diplocraterion isp.,) and vertical borings typical of consolidated substrates. High-energy sandy contourite deposits are dominated by horizontal deposit-feeder traces and the development of ichnofabrics with Planolites isp., and Thalassinoides isp. The record of ichnofabrics with slightly deformed Planolites in the interbeds of sandy contourites or in the transition between the facies reveals variations in sedimentation in the bi-gradational contourite succession, and can potentially act as an indicator of depositional hiatus.

A deposit-feeder sea cucumber also ingests suspended particles through the mouth

Although the sea cucumber Apostichopus japonicus has been characterised as a deposit feeder, nutrients sourced from the water column have been recorded in the intestines of this species. However, the mechanisms whereby nutrients in the water enter the intestinal tract of A. japonicus, and whether other suspended particles can be ingested via the mouth of A. japonicus adults, remain unknown. Here, we reveal how A. japonicus ingests suspended particles through the mouth. We used synthetic particles and video recording to confirm the suspension uptake by the sea cucumber. A. japonicus continued to ingest suspended particles (if present) over time, and the particle-ingestion rate was positively correlated with the concentration of suspended particles (Pearson correlation: r=0.808). Additionally, clearance rates of the suspended particles ranged from 0.3–0.9 L−1 h−1. The findings of this study thus provide evidence of a previously undescribed particle uptake mechanism in a commercially important species.

Contrasting Effects of Bioturbation Studied in Intact and Reconstructed Estuarine Sediments

Macrofauna can produce contrasting biogeochemical effects in intact and reconstructed sediments. We measured benthic fluxes of oxygen, inorganic carbon, and nitrogen and denitrification rates in intact sediments dominated by a filter and a deposit feeder and in reconstructed sediments added with increasing densities of the same organisms. Measurements in reconstructed sediments were carried out 5 days after macrofauna addition. The degree of stimulation of the measured fluxes in the intact and reconstructed sediments was then compared. Results confirmed that high densities of bioturbating macrofauna produce profound effects on sediment biogeochemistry, enhancing benthic respiration and ammonium recycling by up to a factor of ~3 and ~9, respectively, as compared to control sediments. The deposit feeder also increased total denitrification by a factor of ~2, whereas the filter feeder activity did not stimulate nitrogen removal. Moreover, the effects of deposit feeders on benthic fluxes were significantly higher (e.g., on respiration and ammonium recycling) or different (e.g., on denitrification) when measured in intact and reconstructed sediments. In intact sediments, deposit feeders enhanced the denitrification coupled to nitrification and had no effects on the denitrification of water column nitrate, whereas in reconstructed sediments, the opposite was true. This may reflect active burrowing in reconstructed sediments and the long time needed for slow growing nitrifiers to develop within burrows. Results suggest that, in bioturbation studies, oversimplified experimental approaches and insufficient preincubation time might lead to wrong interpretation of the role of macrofauna in sediment biogeochemistry, far from that occurring in nature.

IDENTIFIKASI KESESUAIAN LAHAN BUDIDAYA TERIPANG PASIR (Holothuria scabra) BERDASARKAN PARAMETER KIMIA MENGGUNAKAN SISTEM INFORMASI GEOGRAFIS DI PERAIRAN LOMBOK BARAT

Teripang merupakan kelompok hewan invertebrata dari filum Echinodermata kelas Holothurioidea. Teripang termasuk komponen penting dalam rantai makanan karena peranannya sebagai pemakan endapan (deposit feeder) dan pemakan materi tersuspensi (suspension feeder). Oleh karena itu diperlukan informasi yang memadai yang bisa dipakai untuk pengelolaan teripang secara berkelanjutan. Salah satu metode yang digunakan adalah dengan menggunakan sistem informasi geografis (SIG). Metode ini dapat digunakan untuk memudahkan dalam mengetahui lokasi penyebarannya, sehingga pengembangan dalam kegiatan budidaya teripang pasir (Holothuria scabra) dapat tercapai dengan optimal. Tujuan penelitian ini adalah menganalisis kesesuaian kawasan budidaya teripang menggunakan Aplikasi SIG yang disajikan dalam bentuk peta kesesuaian kawasan budidaya teripang pasir (H. scabra) di Perairan Lombok Barat. Penelitian ini dilaksanakan pada tanggal 17 Oktober 2016 – 27 November 2016 di Gili Asahan, Gili Layar dan Gili Gede Kecamatan Sekotong Barat Kabupaten Sekotong Barat Pulau Lombok Provinsi Nusa Tenggara Barat. Pengumpulan data dilakukan dengan metode survei, berupa data primer dan sekunder yang berkaitan langsung dengan hidup teripang. Berdasarkan parameter kimia hasil penelitian di Perairan Lombok Barat adalah: pH 6,82 – 7,50, salinitas 32 – 34 ppt dan DO 6,19 – 6,52 mg/L, lokasi kesesuaian lahan untuk kategori sangat sesuai terdapat di Gili Gede, kategori sesuai di Gili Asahan dan kategori tidak sesuai di Gili Layar.

Preferensi Habitat Spesies Kerang Laut (Moluska: Bivalvia) Di Ekosistem Intertidal Tanjung Bilik Taman Nasional Baluran

Kerang adalah jenis moluska yang hidup di substrat beberapa ekosistem perairan. Kerang merupakan komponen penting yang berperan sebagai pemakan sisa organik yang berada di perairan (deposit feeder) dan pemakan suspensi (suspension feeder) dalam rantai makanan. Beberapa spesies kerang juga dapat berperan dalam mengakumulasi (bioakumulator) logam berat. Di Taman Nasional Baluran, Jawa Timur, Indonesia, kerang sering digunakan oleh masyarakat setempat sebagai bahan dasar makanan dan cangkangnya dijual sebagai dekorasi kamar, perhiasan, dan peralatan rumah tangga. Akibat terjadinya eksploitasi terhadap kerang secara berlebihan, telah diduga bahwa kepadatan populasi dan keanekaragaman spesies kerang telah menurun. Penelitian ini dilakukan pada Oktober 2019 di Pantai Bilik di Taman Nasional Baluran untuk menentukan komposisi spesies dan preferensi habitat spesies kerang. Pengambilan sampel acak digunakan untuk mengukur komposisi spesies kerang di daerah penelitian. Hasil analisis menunjukkan bahwa terdapat adanya 6 ordo, 8 famili, 11 genera, dan 14 spesies. Nilai keanekaragaman spesies yang dihitung menggunakan indeks keanekaragaman jenis (H'). Hasil yang diperoleh menunjukkan telah ditemukan 2,109, yang menunjukkan keanekaragaman spesies tingkat sedang. Analisis kemerataan spesies menunjukkan nilai sebesar 0,79, yang berarti kemerataan spesies rendah. Habitat kerang di Pantai Bilik lebih terfokus pada bongkahan karang mati yang ditumbuhi alga. Moluska sering ditemukan bersama dengan karang dari keluarga Faviidae, terutama yang berasal dari genus Porites.