Coastal zones as important habitats of coccolithophores: A study of species diversity, succession, and life‐cycle phases

Abstract

Coccolithophores are unicellular calcifying eukaryotes with a complex life‐cycle; they are important primary producers, and major drivers of global biogeochemical cycles. The majority of research on coccolithophores has been focused on open ocean waters, while the knowledge of their roles in coastal ecosystems is limited. Early 20th century studies of the Adriatic coast produced major taxonomic papers describing half of the projected diversity of coccolithophores. Afterwards, there have been only scarce records of their diversity and ecology in the Adriatic, and coastal systems in general. We aimed to assess coccolithophore diversity and species succession, and closely examine their ecological preferences in the coastal area of the northern Adriatic. We recorded coccolithophores throughout the year at 100% frequency, documented 52 taxa, abundances as high as 2.4 × 105 cells L−1, and noted the winter domination over the phytoplankton community. Out of 52 observed coccolithophore taxa, 31 were heterococcolithophorids and 21 holococcolithophorids. Moreover, seven pairs of heterococcolith and holococcolith phases were noted, and two strategies of temporal separation of life‐cycle phases were observed. We report ecological preferences of those life‐cycle pairs and give in situ evidence that holo‐ and heterococcolith phases are widening the specie's ecological niches. This expansion allows the species to exploit a wider range of ecological conditions and enables phenotypic plasticity, important in response to changes in the environment. With this study we emphasize that coastal areas are highly productive for coccolithophore studies. Our results indicate that a shift in research effort on coccolithophores in the coastal waters is needed.

Phytoplankton temporal dynamics in the coastal waters of the north-eastern Adriatic Sea (Mediterranean Sea) from 2010 to 2017

“…However, Mozetić et al (2012) and Marić et al (2012) observed a strong reduction in amplitude of this bloom from the period 1989-2002to 2003and from 1972 and some large diatoms (Dactyliosolen blavyanus, Lioloma pacificum, Guinardia striata, Asterionellopsis glacialis) were typical of this period. The presence of coccolithophores in autumn assemblages has already been reported in the eastern Adriatic Sea (Šupraha et al 2011;Cabrini et al 2012;Cerino et al 2017;Godrijan et al 2018;Skejić et al 2018). In general, autumn coccolithophores are related to high nutrient concentrations (Godrijan et al 2013), as indicated by the positive correlation between coccolithophores and phosphate concentration.…”

“…Generally, non-redtide dinoflagellates are reported to be well-adapted to thermal stratification conditions with low nutrient availability (Latasa et al 2010). The coccolithophore Rhabdolithes claviger was also identified as a distinctive summer coccolithophore in the Adriatic Sea (Bernardi Aubry et al 2006;Godrijan et al 2013;Cerino et al 2017;Godrijan et al 2018) as well as in other Mediterranean areas (Cros and Fortuño 2002;Dimiza et al 2015;Karatsolis et al 2017) and in thermal stratified waters worldwide (Okada and McIntyre 1977;Hagino et al 2000). It is reported to be related to high temperature and low nitrate concentrations (Haidar and Thierstein 2001;Bernardi Aubry et al 2006;Godrijan et al 2013).…”

Mixotrophic uptake of organic compounds by coccolithophores

“…The process of haploidization and reduction of genome size by half probably requires major reorganization in the pattern of gene expression, leading to the creation of two largely different cellular types (De Vargas and Probert ). Moreover, the expansion of the ecological niches by different life strategies may be particularly appropriate for survival in ecosystems with fluctuating nutrient availability (Godrijan et al ). We noted a difference between organic uptake by haploid and diploid phases in Isochrysidales and Coccolithales orders.…”

The haplo-diplontic life cycle expands niche space of coccolithophores

“…Coccolithophore abundance measurements were compiled from 36 studies, constituting 2534 measurements, and representing all major oceans (Table 1). These studies utilized scanning electron microscopy (SEM) to enumerate or further identify coccolithophores rather than soley relying on the more commonly utilized light or cross polarized microscopy which under-represents coccolithophore biodiversity (Godrijan et al, 2018), in particular holococcolithophores (Bollmann et al, 2002;Cerino et al, 2017). We used this data set to investigate global, and vertical distribution patterns of haploid and diploid coccolithophore life cycle phases, specifically focusing on holococcolith forming species.…”

“…While niche differentiation has been widely observed for haplo-diplontic seaweeds (Couceiro et al, 2015;Guillemin et al, 2013;Lees et al, 2018;Lubchenco and Cubit, 1980), and coccolithophores (Houdan et al, 2006;Cros and Estrada, 2013;Godrijan et al, 2018;Frada et al, 2018), to-date no research has quantitatively investigated the extent of niche overlap and niche expansion for haplo-diplontic algae. For coccolithophores this is because research has primarily focused on the diploid life phases, and relatively little is known in regards to the haploid life phase (Taylor et al, 2017;Frada et al, 2018).…”