Cladoceran-inferred environmental change during the LGM to Holocene transition from Onepoto maar paleolake, Auckland, New Zealand

Abstract

Subfossil cladocerans have rarely been used for paleoenvironmental reconstruction from New Zealand lake sediments, and here we detail the first examination of the response of cladocerans to past environments from an Auckland maar paleolake. Cladoceran remains were examined in the upper 230 cm of the lacustrine sediments spanning c. 9Á31 cal. ka BP from Onepoto maar during which time the lake underwent significant changes. Lake level was relatively high during the Last Glacial Coldest Period (c. 28Á18 cal. ka BP), with limited forest in the catchment, shoreline vegetation and low water temperature indicated by the presence of a planktonic taxon, Bosmina meridionalis, and a cold tolerant chydorid cladoceran Alona sp. (affinis type). However, the climate during the last glacial termination after c. 17.9 cal. ka BP changed abruptly, perhaps becoming extremely dry and windy, resulting in increased production of cladoceran resting eggs. Between c. 17.6 and 14.1 cal. ka BP, a gradually ameliorating climate with sustained windiness and dryness might have been unfavourable for hatching of chydorid cladoceran eggs and their recolonisation. After c. 14.1 cal. ka BP, continued climatic amelioration was accompanied by reduced lake levels inferred from high cladoceran littoral: planktonic ratios as well as increased cladoceran diversity and abundance of less cold tolerant chydorid taxa: Alona guttata, Alona sp. (intermedia type) and Alonella excisa. At c. 9 cal. ka BP, the maar crater rim was breached by the marine waters commensurate with postglacial sea-level rise, resulting in degraded water quality and production of a large number of cladoceran ephippia in the sediments.

Biogeography and taxonomy of New Zealand Cladocera (Anomopoda, Chydoridae): a review

“…For example, a similar species has been documented as Biapertura macrocopa in Australia (Sinev 2004). From a maar lake in Auckland, New Zealand, Kattel & Augustinus (2010) reported large Alona-like species with a resemblance to the northern hemisphere species Alona affinis Leydig, 1860. However, it is possible that this specimen belongs to the Biapertura group of the southern hemisphere.…”

“…Until recently C. sphaericus was one of the commonly documented chydorid Cladocera in New Zealand lakes (Burns et al 1984;Kattel & Augustinus 2010). However, Frey (1980a) argued that C. sphaericus may have two species groups, each with an unknown number of species worldwide.…”

“…The record of small Alona such as Alona guttata Sars, 1862 in Auckland maar lake sediments suggests that they have been present in New Zealand for at least the past 30 cal kyr BP and became dominant during the early Holocene (Kattel & Augustinus 2010). Both modern and fossil populations of Alona guttata Sars, 1862 have been recorded in regions with sub-zero temperatures such as Arctic Greenland (Frey 1991b) and the alpine Himalayas (Swar & Fernando 1979;Fernando & Kanduru 1984), mild northern and southern temperate regions of the USA (Harmsworth 1968) and New Zealand (Burger et al 2002;Kattel & Augustinus 2010), as well as in the tropics of Brazil (Santos-Wisniewski et al 2001).…”

“…Both modern and fossil populations of Alona guttata Sars, 1862 have been recorded in regions with sub-zero temperatures such as Arctic Greenland (Frey 1991b) and the alpine Himalayas (Swar & Fernando 1979;Fernando & Kanduru 1984), mild northern and southern temperate regions of the USA (Harmsworth 1968) and New Zealand (Burger et al 2002;Kattel & Augustinus 2010), as well as in the tropics of Brazil (Santos-Wisniewski et al 2001). Fryer (1968 reported that, unlike other small Alona, A. guttata occurs in both large lakes and small ponds and is tolerant of a wide range of physicochemical conditions.…”

“…The chydorid body parts such as head shield, post abdomen, carapace, ephippium and post-abdominal claws are then examined under a microscope at 100) and 400) magnification. Based on morphological characters of the body parts, the taxonomy of chydorids is identified (Frey 1986;Korhola & Rautio 2001;Kattel & Augustinus 2010).…”