Zooplankton can serve as indicators of ecosystem health, water quality, food web structure, and environmental change, including those associated with climate change and ocean acidification (OA). Laboratory studies demonstrate that low pH and high pCO2 associated with OA can significantly affect the physiology and survival of zooplankton, with differential responses among taxa. While laboratory studies can be indicative of zooplankton response to OA, in situ responses will ultimately determine the fate of populations and ecosystems. In this perspective, we compare expectations from experimental studies with observations made in Puget Sound (Washington, United States), a highly dynamic estuary with known vulnerabilities to low pH and high pCO2. We found little association between empirical measures of in situ pH and the abundance of sensitive taxa as revealed by meta-analysis, calling into question the coherence between experimental studies and field observations. The apparent mismatch between laboratory and field studies has important ramifications for the design of long-term monitoring programs and interpretation and use of the data produced. Important work remains to be done to connect traits that are sensitive to OA with those that are ecologically relevant and reliably observable in the field.
In coastal marine environments, physical and biological forces can cause dynamic pH fluctuations from microscale (diffusive boundary layer [DBL]) up to ecosystem‐scale (benthic boundary layer [BBL]). In the face of ocean acidification (OA), such natural pH variations may modulate an organism’s response to OA by providing temporal refugia. We investigated the effect of pH fluctuations, generated by the brown alga Fucus serratus‘ biological activity, on the calcifying epibionts Balanus improvisus and Electra pilosa under OA. For this, both epibionts were grown on inactive and biologically active surfaces and exposed to (1) constant pH scenarios under ambient (pH 8.1) or OA conditions (pH 7.7), or (2) oscillating pH scenarios mimicking BBL conditions at ambient (pH 7.7–8.6) or OA scenarios (pH 7.4–8.2). Furthermore, all treatment combinations were tested at 10°C and 15°C. Against our expectations, OA treatments did not affect epibiont growth under constant or fluctuating (BBL) pH conditions, indicating rather high robustness against predicted OA scenarios. Furthermore, epibiont growth was hampered and not fostered on active surfaces (fluctuating DBL conditions), indicating that fluctuating pH conditions of the DBL with elevated daytime pH do not necessarily provide temporal refugia from OA. In contrast, results indicate that factors other than pH may play larger roles for epibiont growth on macrophytes (e.g., surface characteristics, macrophyte antifouling defense, or dynamics of oxygen and nutrient concentrations). Warming enhanced epibiont growth rates significantly, independently of OA, indicating no synergistic effects of pH treatments and temperature within their natural temperature range.
Physiological responses to ocean acidification are thought to be related to energetic trade‐offs. Although a number of studies have proposed that negative responses to low pH could be minimized in situations where food resources are more readily available, evidence for such effects on individuals remain mixed, and the consequences of such effects at the community level remain untested. We explored the potential for food availability and diet quality to modify the effects of acidification on developing marine fouling communities in field‐deployed mesocosms by supplementing natural food supply with one of two species of phytoplankton, differing in concentration of fatty acids. After twelve weeks, no species demonstrated the interactive effects generally predicted in the literature, where a positive overall effect of diet mitigated the negative overall effects of acidification. Rather, for some species, additional food supply appeared to bring out or exacerbate the negative effects of low pH. Community richness and structure were only altered by acidification, while space occupation and evenness reflected patterns of the most dominant species. Importantly, we find that acidification stress can increase the relative abundance of invasive species, even under resource conditions that otherwise prevented invasive species establishment. Overall, the proposed hypothesis regarding the ability for food addition to mitigate the negative effects of acidification is thus far not widely supported at species or community levels. It is clear that acidification is a strong driving force in these communities but understanding underlying energetic and competitive context is essential to developing mechanistic predictions for climate change responses.
Ocean acidification (OA) affects marine biodiversity and alters the structure and function of marine populations, communities, and ecosystems. Recently, effects of OA on the behavioral responses of marine animals have been given with much attention. While many of previous studies focuses on marine fish. Evidence suggests that marine invertebrate behaviors were also be affected. In this review, we discussed the effects of C02-driven OA on the most common behaviors studied in marine invertebrates, including settlement and habitat selection, feeding, anti-predatory, and swimming behaviors, and explored the related mechanisms behind behaviors. This review summarizes how OA affects marine invertebrate behavior, and provides new insights and highlights novel areas for future research.
Bryozoans are aquatic animals that form colonies of connected individuals. Bryozoans have such highly variable morphology that they are often mistaken for other organisms such as hydroids, corals, colonial ascidians and turfing seaweeds. Some colonies are bushy and moss-like, hence the phylum name, Bryozoa, which means ‘moss animals’ in Greek. Others are flat and encrusting, hence the common name ‘sea mats’. Still others resemble lace, forming erect frondose colonies with holes in their structure or encrustations over sea-weeds and rocks, hence the name ‘lace corals’. Since no single common name is applicable to all species, the name ‘bryozoans’ is the most preferred by researchers of the group.
- Seaweeds are able to modify the chemical environment at their surface, in a micro‐zone called the diffusive boundary layer (DBL), via their metabolic processes controlled by light intensity. Depending on the thickness of the DBL, sessile invertebrates such as calcifying bryozoans or tube‐forming polychaetes living on the surface of the blades can be affected by the chemical variations occurring in this microlayer. Especially in the context of ocean acidification (OA), these microhabitats might be considered as a refuge from lower pH, because during the day photosynthesis temporarily raises the pH to values higher than in the mainstream seawater.
- We assessed the thickness and the characteristics of the DBL at two pH levels (today’s average surface ocean pH 8.1 and a reduced pH predicted for the end of the century, pH 7.7) and seawater flows (slow, 0.5 and fast, >8 cm/s) on Ecklonia radiata (kelp) blades. Oxygen and pH profiles from the blade surface to the mainstream seawater were measured with O2 and pH microsensors for both bare blades and blades colonized by the bryozoan Membranipora membranacea.
- The DBL was thicker in slow flow compared with fast flow and the presence of bryozoans increased the DBL thickness and shaped the DBL gradient in dark conditions. Net production was increased in the low pH condition, increasing the amount of oxygen in the DBL in both bare and epiphytized blades. This increase drove the daily pH fluctuations at the blade surface, shifting them towards higher values compared with today’s pH. The presence of bryozoans led to lower oxygen concentrations in the DBL and more complex pH fluctuations at the blade surface, particularly at pH 7.7.
- Overall, this study, based on microprofiles, shows that, in slow flow, DBL microenvironments at the surface of the kelps may constitute a refuge from OA with pH values higher than those of the mainstream seawater. For calcifying organisms, it could also represent training ground for harsh conditions, with broad daily pH and oxygen fluctuations. These chemical microenvironments, biologically shaped by the macrophytes, are of great interest for the resilience of coastal ecosystems in the context of global change.
Ocean acidification may have far-reaching consequences for marine community and ecosystem dynamics, but its full impacts remain poorly understood due to the difficulty of manipulating pCO2 at the ecosystem level to mimic realistic fluctuations that occur on a number of different timescales. It is especially unclear how quickly communities at various stages of development respond to intermediate-scale pCO2 change and, if high pCO2 is relieved mid-succession, whether past acidification effects persist, are reversed by alleviation of pCO2 stress, or are worsened by departures from prior high pCO2 conditions to which organisms had acclimatized. Here, we used reciprocal transplant experiments along a shallow water volcanic pCO2 gradient to assess the importance of the timing and duration of high pCO2 exposure (i.e. discrete events at different stages of successional development vs. continuous exposure) on patterns of colonization and succession in a benthic fouling community. We show that succession at the acidified site was initially delayed (less community change by eight weeks) but then caught up over the next four weeks. These changes in succession led to homogenization of communities maintained in or transplanted to acidified conditions, and altered community structure in ways that reflected both short- and longer-term acidification history. These community shifts are likely a result of interspecific variability in response to increased pCO2 and changes in species interactions. High pCO2 altered biofilm development, allowing serpulids to do best at the acidified site by the end of the experiment, although early (pre-transplant), negative effects of pCO2 on recruitment of these worms was still detectable. The ascidians Diplosoma sp. and Botryllus sp. settled later and were more tolerant to acidification. Overall, transient and persistent acidification-driven changes in the biofouling community, via both past and more recent exposure, could have important implications for ecosystem function and food web dynamics.
Marine invertebrates with skeletons made of high-magnesium calcite may be especially susceptible to ocean acidification (OA) due to the elevated solubility of this form of calcium carbonate. However, skeletal composition can vary plastically within some species, and it is largely unknown how concurrent changes in multiple oceanographic parameters will interact to affect skeletal mineralogy, growth and vulnerability to future OA. We explored these interactive effects by culturing genetic clones of the bryozoan Jellyella tuberculata (formerly Membranipora tuberculata) under factorial combinations of dissolved carbon dioxide (CO2), temperature and food concentrations. High CO2 and cold temperature induced degeneration of zooids in colonies. However, colonies still maintained high growth efficiencies under these adverse conditions, indicating a compensatory trade-off whereby colonies degenerate more zooids under stress, redirecting energy to the growth and maintenance of new zooids. Low-food concentration and elevated temperatures also had interactive effects on skeletal mineralogy, resulting in skeletal calcite with higher concentrations of magnesium, which readily dissolved under high CO2. For taxa that weakly regulate skeletal magnesium concentration, skeletal dissolution may be a more widespread phenomenon than is currently documented and is a growing concern as oceans continue to warm and acidify.
Few studies to date have investigated the effects of ocean acidification on non-reef forming marine invertebrates with non-feeding larvae. Here, we exposed adults of the bryozoan Bugula neritina and their larvae to lowered pH. We monitored spawning, larval swimming, settlement, and post-settlement individual sizes at two pHs (7.9 vs. 7.6) and settlement dynamics alone over a broader pH range (8.0 down to 6.5). Our results show that spawning was not affected by adult exposure (48 h at pH 7.6), larvae swam 32% faster and the newly-settled individuals grew significantly larger (5%) at pH 7.6 than in the control. Although larvae required more time to settle when pH was lowered, reduced pH was not lethal, even down to pH 6.5. Overall, this fouling species appeared to be robust to acidification, and yet, indirect effects such as prolonging the pelagic larval duration could increase predation risk, and might negatively impact population dynamics.
Many aquatic animals grow into colonies of repeated, genetically identical, modules (zooids). Zooid interconnections enable colonies to behave as integrated functional units, while plastic responses to environmental changes may affect individual zooids. Plasticity includes the variable partitioning of resources to sexual reproduction, colony growth and maintenance. Maintenance often involves regeneration, which is also a routine part of the life history in some organisms, such as bryozoans. Here we investigate changes in regenerative capacity in the encrusting bryozoan Cryptosula pallasiana when cultured at different seawater pCO2 levels. The proportion of active zooids showing polypide regeneration was highest at current oceanic pH (8.1), but decreased progressively as pH declined below that value, reaching a six-fold reduction at pH 7.0. The zone of budding of new zooids at the colony periphery declined in size below pH 7.7. Under elevated pCO2 conditions, already experienced sporadically in coastal areas, skeletal corrosion was accompanied by the proportional reallocation of resources from polypide regeneration in old zooids to the budding of new zooids at the edge of the colony. Thus, future ocean acidification can affect colonial organisms by changing how they allocate resources, with potentially profound impacts on life-history patterns and ecological interactions.
Ocean acidification is expected to cause significant changes in the marine environment over the coming century. The effects of acidification on organisms’ physiology have been studied over the past two decades. However, the experimental findings are not always easily comparable because of differences in experimental design, and comparable experiments do not always produce similar results. To rigorously integrate the current knowledge, we performed a meta-analysis of published studies focused on benthic organisms in the Mediterranean Sea, both in controlled manipulative experiments and in situ experiments near vent areas. In each experiment, the effect of acidification was calculated as the log-transformed response ratio (LnRR) of experimental versus control conditions. The quantitative results obtained by the meta-analysis highlight: (a) an increase in fleshy algae cover, which may lead to a competitive advantage over calcifying macroalgae; (b) a reduction of calcification by both algae and corals; (c) an increase in seagrass shoot density under low pH; and (d) a general increase in the photosynthetic activity of macrophytes.
Anthropogenic increase of atmospheric pCO2 since the Industrial Revolution has caused seawater pH to decrease and seawater temperatures to increase—trends that are expected to continue into the foreseeable future. Myriad experimental studies have investigated the impacts of ocean acidification and warming on marine calcifiers’ ability to build protective shells and skeletons. No studies, however, have investigated the combined impacts of ocean acidification and warming on the whole-shell dissolution kinetics of biogenic carbonates. Here, we present the results of experiments designed to investigate the effects of seawater saturation state (ΩA = 0.4 – 4.6) and temperature (10, 25 °C) on gross rates of whole-shell dissolution for ten species of benthic marine calcifiers: the oyster Crassostrea virginicus, the ivory barnacle Balanus eburneus, the blue mussel Mytilus edulis, the conch Strombus alatus, the tropical coral Siderastrea siderea, the temperate coral Oculina arbuscula, the hard clam Mercenaria mercenaria, the soft clam Mya arenaria, the branching bryozoan Schizoporella errata, and the coralline red alga Neogoniolithon sp. These experiments confirm that dissolution rates of whole-shell biogenic carbonates decrease with calcium carbonate (CaCO3) saturation state, increase with temperature, and vary predictably with respect to the relative solubility of the calcifiers’ polymorph mineralogy [high-Mg calcite (mol% Mg > 4) > aragonite > low-Mg calcite (mol% Mg < 4)], consistent with prior studies on sedimentary and inorganic carbonates. Furthermore, the severity of the temperature effects on gross dissolution rates also varied with respect to carbonate polymorph solubility, with warming (10 – 25 °C) exerting the greatest effect on biogenic high-Mg calcite, an intermediate effect on biogenic aragonite, and the least effect on biogenic low-Mg calcite. These results indicate that both ocean acidification and warming will lead to increased dissolution of biogenic carbonates in future oceans, with shells/skeletons composed of the more soluble polymorphs of CaCO3 being the most vulnerable to these stressors. The effects of saturation state and temperature on gross shell dissolution rate were modelled with an exponential asymptotic function (y = B0 – B2· eB1·x) that appeals to the general Arrhenius-derived rate equation for mineral dissolution [r = (C · e-Ea/RT)(1-Ω)n]. Although the dissolution curves for the investigated biogenic CaCO3 exhibited exponential asymptotic trends similar to those of inorganic CaCO3, the observation that gross dissolution of whole-shell biogenic CaCO3 occurred (albeit at lower rates) even in treatments that were oversaturated (Ω > 1) with respect to both aragonite and calcite reveals fundamental differences between the dissolution kinetics of whole-shell CaCO3 and inorganic CaCO3. Thus, applying stoichiometric solubility products derived for inorganic CaCO3 to model gross dissolution of biogenic carbonates may substantially underestimate the impacts of ocean acidification on net calcification (gross calcification minus gross dissolution) of systems ranging in scale from individual organisms to entire ecosystems (i.e., net ecosystem calcification). Finally, these experiments permit rough estimation of the impact of CO2-induced ocean acidification on the gross calcification rates of various marine calcifiers, calculated as the difference between net calcification rates derived empirically in prior studies and gross dissolution rates derived from the present study. Organisms’ gross calcification responses to acidification were generally less severe than their net calcification response patterns, with aragonite mollusks (bivalves, gastropods) exhibiting the most negative gross calcification response to acidification, and photosynthesizing organisms, including corals and coralline red algae, exhibiting relative resilience.
1.Increasing levels of CO2 in the atmosphere are affecting ocean chemistry, leading to increased acidification (i.e., decreased pH) and reductions in calcium carbonate saturation state. 2.Many species are likely to respond to acidification, but the direction and magnitude of these responses will be based on interspecific and ontogenetic variation in physiology and the relative importance of calcification. Differential responses to ocean acidification among species will likely result in important changes in community structure and diversity. 3.To characterize potential impacts of ocean acidification on community composition and structure, we examined the response of a marine fouling community to experimental CO2 enrichment in field-deployed flow-through mesocosm systems. 4.Acidification significantly altered community structure by altering the relative abundances of species and reduced community variability, resulting in more homogenous biofouling communities from one experimental tile to the next both among and within the acidified mesocosms. Mussel (Mytilus trossulus) recruitment was reduced by over 30% in the elevated CO2 treatment compared to the ambient treatment by the end of the experiment. Strong differences in mussel cover (up to 40% lower in acidified conditions) developed over the second half of the 10-week experiment. Acidification did not appear to affect mussel growth, as average mussel sizes were similar between treatments at the end of the experiment. Hydroid (Obelia dichotoma) cover was significantly reduced in the elevated CO2 treatment after eight weeks. Conversely, the percent cover of bryozoan colonies (Mebranipora membranacea) was higher under acidified conditions with differences becoming apparent after six weeks. Neither recruitment nor final size of barnacles (Balanus crenatus) was affected by acidification. By the end of the experiment, diversity was 41% lower in the acidified treatment relative to ambient conditions. 5.Overall, our findings support the general expectation that OA will simplify marine communities by acting on important ecological processes that ultimately determine community structure and diversity.
Factors related to depth have the potential to provide an analogue for future changes in the skeletal mineralogy of calcifying marine organisms and communities, given that oceanic pH decreases with depth, with a minimum pH of <7.7, which corresponds to the predicted pH of shallow waters in the next 85 yr. Antarctic bryozoans are often characterized by surprisingly broad bathymetrical ranges, and thus have potential for the study of depth-related environmental changes. This study addressed depth-related changes in the levels of magnesium (Mg)-calcite in Antarctic bryozoan skeletons for the first time in order to facilitate predictions of ocean acidification effects. Specimens (n = 103) belonging to 4 bryozoan species (3 cheilostomes and 1 cyclostome) were collected at various depths in East Antarctica (Terre Adelie and George V Land) during the CEAMARC cruise (December 2007 to January 2008), and Mg-calcite contents from their calcareous skeletons were studied using X-ray diffraction. A dataset was compiled from existing environmental data for both sampling and neighboring sites. All 4 species were found to be entirely calcitic with low or intermediate Mg-levels. The predicted negative correlation between pH and Mg-calcite was not evident. Higher Mg levels were found in Fasciculipora ramosa from the George V Basin, suggesting that high salinity shelf water creates favorable conditions for this species, although alternative environmental and biological factors influencing Mg-calcite in skeletons are also discussed for this species.
The bulk dissolution rates of six biogenic carbonates (goose barnacle, benthic foraminifera, bryozoan, sea urchin, and two types of coralline algae) and a sample of mixed sediment from the Bermuda carbonate platform were measured in natural seawater at pCO2 values ranging from approximately 3000 to 5500 μatm. This range of pCO2 values encompassed values regularly observed in porewaters at a depth of a few cm in carbonate sediments at shallow water depths (<15 m) on the Bermuda carbonate platform. The biogenic carbonates included calcites of varying Mg content (2–17 mol%) and a range of specific surface areas (0.01–2.7 m2 g−1) as determined by BET gas adsorption. Measured rates of dissolution increased with increasing pCO2 treatment for all substrates and ranged from 2.5 to 18 μmol g−1 h−1. The highest rates of dissolution were observed for the bryozoans and the lowest rates for the goose barnacles. The relative ranking in dissolution rates between different substrates was consistent at all pCO2 levels, indicating that substrates dissolve sequentially and that some substrates will be more vulnerable than others to rising CO2 and ocean acidification. Furthermore, dissolution rates were found to increase with increasing Mg content, though the relative dissolution rates were observed to be a function of both Mg content and microstructure (surface area).
Bryozoans are colonial animals that are widely distributed in marine benthic environments and play an important role in temperate and cold-water oceanic shelves as habitat providers. Morphologically and mineralogically diverse, bryozoans are important carbonate producers with an extensive fossil record, which makes them good indicators in environmental and (paleo) environmental research. Existing data, though insufficient, suggests that bryozoans can become a valuable tool in investigating present-day climate change. This paper reviews the major characteristics of bryozoans, their function in shallow oceanic areas worldwide, and their potential as proxy organisms in climate and ocean acidification research.
Ocean acidification (OA) is today considered one of the most pervasive stressors for marine biota at the level of species, communities and ecosystems. Naturally acidified systems, such as the CO2 vents, represent suitable laboratories to study the effects of OA on benthic organisms. An analysis of the colonization pattern of epibionts settled on artificial leaves (mimics) of Posidonia oceanica in relation to ocean acidification at the shallow CO2 vents off the island of Ischia, is here presented. Mimics of Posidonia oceanica artificial leaves (dark green flexible PVC stripes 1 cm wide x 36 cm long) were placed from September 2009 to September 2010 along a gradient of OA of the Ischia vent’s system at six stations (3 on the south and 3 on the north side of the study area), located at extreme low pH (mean pH 7.5), low pH (7.8), and control, normal pH conditions (8.12). Six artificial leaves per station were collected every three months and analysed for taxa identification and estimates of coverage (algae and sessile clonal invertebrates) and number of individuals (not clonal taxa). Patterns of colonization in control stations showed a progressive increase in time in coverage values of many organisms, mainly calcifying forms as coralline algae, which represent the dominant taxon, spirorbids and bryozoans. Colonization of artificial leaves located in low pH stations followed a similar temporal pattern as control conditions, but with lower coverage and higher patchiness of calcareous forms at 12 months of colonization. Epibionts in extreme low pH conditions were dominated by filamentous green/brown algae, with the occurrence of a few coralline algae, spirorbids and bryozoans, especially in the early months of colonization (3 and 6 months). Colonization at 9 and 12 months showed the disappearance of even these rare calcareous organisms and occurrence only of filamentous turf and fleshy algae, with a very simplified epibiont assemblage, remaining at an early, young colonization stage. These results indicate a strong selection of calcareous forms and the lack of successional stages in extreme low pH conditions, while the few calcifiers settled at short exposure time (3-6 months) do not seem to survive at longer exposure to critical values of OA.
Understanding is currently limited of the biological processes underlying the responses of modular organisms to climate change and the potential to adapt through morphological plasticity related to their modularity. Here, we investigate the effects of ocean acidification and seawater warming on the growth, life history and morphological plasticity in the modular bryozoan Calpensia nobilis using transplantation experiments in a shallow Mediterranean volcanic CO2 vents system that simulates pH values expected for the year 2100. Colonies exposed at vent sites grew at approximately half the rate of those from the control site. Between days 34 and 48 of the experiment, they reached a possible ‘threshold’, due to the combined effects of exposure time and pH. Temperature did not affect zooid length, but longer zooids with wider primary orifices occurred in low pH conditions close to the vents. Growth models describing colony development under different environmental scenarios suggest that stressed colonies of C. nobilis reallocate metabolic energy to the consolidation and strengthening of existing zooids. This is interpreted as a change in life-history strategy to support persistence under unfavourable environmental conditions. Changes in the skeletal morphology of zooids evident in C. nobilis during short-time (87 days) exposure experiments reveal morphological plasticity that may indicate a potential to adapt to the more acidic Mediterranean predicted for the future.
Many animal phyla have the physiological ability to produce biomineralized skeletons with functional roles that have been shaped by natural selection for more than 500 million years. Among these are bryozoans, a moderately diverse phylum of aquatic invertebrates with a rich fossil record and importance today as bioconstructors in some shallow-water marine habitats. Biomineralizational patterns and, especially, processes are poorly understood in bryozoans but are conventionally believed to be similar to those of the related lophotrochozoan phyla Brachiopoda and Mollusca. However, bryozoan skeletons are more intricate than those of these two phyla. Calcareous skeletons have been acquired independently in two bryozoan clades – Stenolaemata in the Ordovician and Cheilostomata in the Jurassic – providing an evolutionary replicate. This review aims to highlight the importance of biomineralization in bryozoans and focuses on their skeletal ultrastructures, mineralogy and chemistry, the roles of organic components, the evolutionary history of bimineralization in bryozoans with respect to changes in seawater chemistry, and the impact of contemporary global changes, especially ocean acidification, on bryozoan skeletons. Bryozoan skeletons are constructed from three different wall types (exterior, interior and compound) differing in the presence/absence and location of organic cuticular layers. Skeletal ultrastructures can be classified into wall-parallel (i.e. laminated) and wall-perpendicular (i.e. prismatic) fabrics, the latter apparently found in only one of the two biomineralizing clades (Cheilostomata), which is also the only clade to biomineralize aragonite. A plethora of ultrastructural fabrics can be recognized and most occur in combination with other fabrics to constitute a fabric suite. The proportion of aragonitic and bimineralic bryozoans, as well as the Mg content of bryozoan skeletons, show a latitudinal increase into the warmer waters of the tropics. Responses of bryozoan mineralogy and skeletal thickness to oscillations between calcite and aragonite seas through geological time are equivocal. Field and laboratory studies of living bryozoans have shown that predicted future changes in pH (ocean acidification) combined with global warming are likely to have detrimental effects on calcification, growth rate and production of polymorphic zooids for defence and reproduction, although some species exhibit reasonable levels of resilience. Some key questions about bryozoan biomineralization that need to be addressed are identified.