Recruitment of Arctic deep‐sea invertebrates: Results from a long‐term hard‐substrate colonization experiment at the Long‐Term Ecological Research observatory HAUSGARTEN

Abstract

For benthic marine invertebrates, recruitment strongly influences the composition and abundance of resulting communities. We present the results of a long‐term (1999–2017) colonization experiment at the Long‐Term Ecological Research observatory HAUSGARTEN in the Fram Strait (Arctic Ocean, 79°N, 04°E, 2500 m water depth). Recruitment panels were constructed from plastic and brick and deployed attached to a metal frame in 1999. The experiment was monitored using a remotely operated vehicle in 2003 and 2011 and recovered in 2017. Recruitment was very low, with only foraminiferans being visible after 4 yr (2003) and one metazoan species, the hydroid Halisiphonia arctica, being visible on the panels after 12 yr (2011). After 18 yr underwater, panels were colonized by 13 metazoan species as well as calcareous and agglutinating foraminiferans. Recruitment was higher on brick panels than on plastic, but while some species were more common on panels at higher altitude (H. arctica and the crinoid Bathycrinus carpenterii), others were more common on panels closer to the seafloor (serpulid polychaetes) or on panels in line with the predominant bottom current (small round white sponges). The most common species recruiting to our panels can be described as opportunistic. Meanwhile, large hexactinellid sponges that are common in natural communities did not recruit to our panels. These results suggest that community assembly in the Arctic deep sea takes much longer than the two decades spanned by this study.

Temporal Trends in Marine Litter at Three Stations of the HAUSGARTEN Observatory in the Arctic Deep Sea

“…Table 6 shows a comparison of litter densities and the proportion of plastics among studies on the deep seafloor. Most of the items recorded were only observed once and may have been eaten or moved by epibenthic organisms or bottom currents (on average 7.8 ± 0.9 cm s −1 , Meyer-Kaiser et al, 2019). Fragmentation into smaller sizes including microplastics is another possibility although environmental conditions in the deep sea such as low temperatures, the absence of UV light and weak currents may slow down this process compared with other realms.…”

Ontogenetic development of the crinoidPoliometra prolixain the Arctic deep sea

“…In particular, the process of metamorphosis from the cystidean to the pentacrinoid stage is similar across most feather stars, with the orals giving rise to the brachials and the basals and radials forming the calyx (Amemiya et al, 2016; Barbaglio et al, 2012; Comeau et al, 2017; Haig & Rouse, 2008; Pertossi et al, 2019). In fact, our specimens were previously (incorrectly) identified as Bathycrinus carpenterii (Comatulida: Bourgueticrininae) by Meyer‐Kaiser et al, (2019) because of a strong resemblance to the cystidean of B. gracilis described by A.M. Clark (1977). Diagnostic characteristics that allowed the identification of our specimens as P. prolixa were only apparent in the oldest pentacrinoid specimens.…”

“…Specimens were collected in the LTER (Long‐Term Ecological Research) observatory HAUSGARTEN in the eastern Fram Strait (Soltwedel et al, 2005, 2015). Cystidean and pentacrinoid stages of Poliometra prolixa were collected on panels as part of a recruitment experiment at 79°4’N, 4°8’E, 2467 m depth (Figure 1; Meyer‐Kaiser et al, 2019). The recruitment experiment consisted of a hexagonal metal frame (1.6 m high, 90 cm on a side) with 20 brick (24 × 11.5 cm) and 20 Perspex panels (25 × 25 cm) at heights of 25, 60, and 90 cm above the seafloor.…”

“…The recruitment experiment consisted of a hexagonal metal frame (1.6 m high, 90 cm on a side) with 20 brick (24 × 11.5 cm) and 20 Perspex panels (25 × 25 cm) at heights of 25, 60, and 90 cm above the seafloor. Adults of P. prolixa were also observed resting on top of the moored metal frame during remotely operated vehicle (ROV) dives to monitor the experiment in 2011 and 2017 (Figure 2; Meyer‐Kaiser et al, 2019). The frame was recovered in 2017 using ROV Kiel 6000 during expedition ARK XXXI/3 (PS108) of R/V Polarstern .…”

“…Our samples include cystidean and pentacrinoids of P. prolixa , collected as part of a long‐term recruitment experiment in the Arctic deep sea (Meyer‐Kaiser et al, 2019). Sessile stages of this species have previously been described and illustrated from a few specimens (Carpenter, 1888; Clark, 1915b, 1921), but our larger collection of specimens in a range of developmental stages allows us to describe the morphology and ontogenetic development in P. prolixa .…”