Recent benthic foraminifera from Twofold Bay, Eden NSW: community structure, biotopes and distribution controls

Abstract

Twofold Bay lies at the confluence of two oceanic boundaries, the near end of the East Australian Current and waters from the Southern Ocean. The Bay is NSW's largest commercial fishing port and has been home to much anthropogenic activity, ranging from whaling, mussel farming, timber export, large boat traffic, Australian Navy activities and recreational fishing. We investigated the sediments and associated foraminifer fauna in the bay and identified four different sedimentological associations linked to local currents and water depths and three foraminiferal associations, with live to dead specimen ratios established for each sample site. Three principal biotopes have been identified using cluster analysis of foraminiferal assemblages, with each biotope characterised by a specific faunal population and substrate type: (1) Inner Bay Biotope, characterised by Elphidium aff. advenum and predominantly very fine-fine sand substrates (63-250 mm); (2) Outer Bay Biotope characterised by Discorbis dimidiatus and medium-coarse sand substrates (250-1000 mm); (3) Harbour Biotope characterised by the widespread species Elphidium advenum macelliforme and bimodal sediments with very fine-coarse silts (2-63 mm) and medium sands (250-500 mm). Substrate type and energy intensity are proposed as limiting factors to foraminiferal distribution and composition. In addition, a short (21 cm long) core obtained from near the entrance of Eden Harbour has been examined in terms of foraminifer assemblages established for the bay. Microfaunal composition shifts clearly correlate with sediment colour changes, while foraminiferal and sedimentary data indicate strong concordant physical and ecological patterns. However, radiocarbon dates from various levels in the core point to sediment disturbance, contradicting this hypothesis. Hence, the dating of the sequence remains problematic.

Foraminiferal biotopes in a shallow continental shelf environment: Esperance Bay (southwestern Australia)

“…(Cann et al, 1988;Hayward et al, 1997). This benthic foraminiferal assemblage was similar to that found in the "Harbour Biotope" of Twofold Bay (Eden, SE Australia; Dean and De Deckker, 2013). Considering the proximity of this area to the entrance of Esperance Harbour, and to hypothesize for this environment that the maritime traffic could have several impacts.…”

“…Benthic foraminiferal studies of the northern Hemisphere are numerous, and they have focused on the distribution and ecology of assemblages in natural and contaminated coastal areas (e.g., Alve and Murray, 1999;Celia Magno et al, 2012;Debenay et al, 2001;Di Bella et al, 2016;Diz and Francés, 2008;Goineau, et al, 2011;Jorissen 1987;Jorissen et al, 1992;Mendes et al, 2004;Milker et al, 2009;Mojtahid et al, 2009;Panieri et al, 2005;Pascual et al, 2008;Salvi et al, 2015;Sgarrella and Moncharmont Zei, 1993). However, the equivalent body of literature for Australia is scarce (Dean and De Deckker, 2013). The clear majority of these studies deals with the distribution of large benthic foraminifera like Amphistegina spp.…”

“…and Marginopora vertebralis (e.g., Doo et al, 2017;Lee et al, 2016b;Prazeres et al, 2017) or investigates the importance of large benthic foraminifera to reef sediment budget and dynamics of the Great Barrier Reef (e.g., Dawson et al, 2014;Renema et al, 2013). Despite these studies, the investigations of the benthic foraminifera assemblages and associated physical and biological parameters that influenced their distribution in the nearshore environments of southern Australia are very limited Dean and De Deckker, 2013;Li et al, 1996;Nash et al, 2010;Quilty and Hosie, 2006;Schröder-Adams et al, 2014).…”

Development of a Training Set of Contemporary Salt-Marsh Foraminifera for Late Holocene Sea- Level Reconstructions in southeastern Australia

“…Other benthic foraminiferal studies from Australia (i.e. Berkeley et al 2008;Cann et al 1993;Dean & De Deckker, 2013;Haslett, 2001;Horton et al 2003;Wang & Chappell, 2001;Woodroffe, 2005) are either located outside of the region of interest, lack elevation data, or use grab samples that are not representative of the surface assemblages.…”