//
you're reading...

Biochemistry

How a whole reef community’s response to OA is impacted by the individual responses of different players

Comeau S., R.C. Carpenter, C.A. Lantz, and P.J. Edmunds: Ocean acidification accelerates dissolution of experimental coral reef communities, Biogeosciences, 12, 365-372, 2015. Doi: 10.5194/bg-12-365/2015

Introduction:

Coral reefs are beautiful, important, natural structures in the tropical oceans that provide a habitat for various fish species and protect the shores of paradises from wave erosion. You probably have already been informed that the rise in atmospheric carbon dioxide (CO2) poses a threat to the survival of reef communities globally; maybe you’ve heard it referred to as “ocean acidification” (OA). The relationship between CO2 and the acidity of the ocean is such: as CO2 in the atmosphere increases some of it dissolves into the ocean, forcing the ocean pH to go down. The fear in the future is that the pH will be forced so low that it could cause the dissolution (chemical breakdown) of coral reefs to exceed their calcification (formation). The long-term effects of OA could be detrimental to the survival of reef communities.

Specific impacts of OA on community structure and the roles of different community members are still vaguely understood. Previous research has observed that there are specie-specific responses to OA. These responses can be used to infer the impact on communities. There have also been observations of in situ communities impacted by volcanic activity and mesocosm research that provide some information of how the community structure may change, however directed research on the response of specific community members to OA and their role in the response of the whole community has had little attention.  To investigate the topic deeper, biologists from California State University set up experiments that enabled them to monitor the response of specific community members and evaluate their roles in the community as a whole to varying concentrations of dissolved CO2.

Methods:

Biologists designed the experiments with an ‘ex situ’ approach so that they could have complete control of the conditions but still apply their research to whole communities found in the natural environment. Four flumes were used to house the ex situ reef communities (figure 1), which were designed with the intention of representing reefs in 3-6 feet of water off the shores of Moorea, French Polynesia.   Species used in the study were chosen to best represent the natural assemblage, they include the four most abundant species of Corals (Porites spp., Porites rus., Montipora spp., and Pocillopora spp.), coralline algae, and dead coral fragments (rubble).

Figure 1: Flume set up.  A) Four tanks outside. B) ex situ reef community in the flume.

Figure 1: Flume set up. A) Four tanks outside. B) ex situ reef community in the flume.

Sediment was taken 200 miles from the reef crest in a lagoon north of Moorea using sediment boxes. The sediment used took a total of four days to collect so that it could re-establish chemical stratification in the boxes before being transferred to the flumes. The importance of including sediment in the flumes is the dissolution that can occur in pore fluid, often related to the CO2 increase from biological activity. There has also been work suggesting that the sediment response to OA can be observed when atmospheric CO2 exceeds 800 uatm.

With this set up scientists were able to manipulate the chemical and physical conditions of the flumes. They set up a pair of flumes to mimic an ambient ocean environment similar to present day (atmospheric CO2 ~400 uatm) and a second pair to mimic conditions based on predictions for the end of this century (atmospheric CO2 ~1300 uatm).  In addition, the flumes were filled with seawater with a controlled flow, pH was monitored and varied to mimic day and night conditions, the flumes were exposed to natural sunlight, and temperatures were maintained at 27 degrees Celsius.

Calcification was measured on three levels: the whole community, the sediment, and the marco-calcifiers (algae and corals) with the intent to distinguish the sensitivity of each to OA. Net calcification rates were calculated using the total alkalinity anomaly method based on a known relationship between alkalinity and calcium carbonate precipitation that allows scientists to use changes in alkalinity to infer changes in calcium carbonate. The whole community was monitored every 7 days and the sediment was monitored at day 7, 30, and 56. Coral and algae rates were determined by subtracting the net sediment calcification from the community calcification.

Results:

Figure 2: Results of whole community (a), sediment (b), and macro-calcifiers (c) between replicate flumes, the ambient and high CO2 conditions and between day and night.

Figure 2: Results of whole community (a), sediment (b), and macro-calcifiers (c) between replicate flumes, the ambient and high CO2 conditions and between day and night.

Researchers were successful in their experiment (figure 2)! The experiment replicated between the duplicate flumes, the researchers were successful at maintaining each pair of flumes at the conditions desired, and they were able to obtain results that compared reasonably to other studies. They did encounter one complication when an outbreak impacted 10% of one coral species in both tanks.   Two of the corals, the least abundant of the four, died. Around 70% of the coralline algae died, but it was attributed to abrasion via sediment

Community:

For the whole community net calcification was higher than dissolution in the ambient flumes during both day and night.   In the high CO2 flumes dissolution was greater than precipitation, but to a greater degree during the night.  Overall calcification was 59% lower in the high CO2 flumes.

Sediment:

The sediment calcification varied between treatments and between day and night. There was net dissolution during both day and night in the high CO2 flumes, and during the night in the ambient CO2 flumes. Overall the sediment in the high CO2 environment experienced net dissolution and the sediment in the ambient flume had a balance between calcification and dissolution.

Corals and Algae (macro-calcifiers):

For corals and algae net calcification was positive in the high CO2 flumes at night and in ambient flumes during the day and night.   Overall there was 29% more net calcification in the ambient CO2 flume than the high CO2 flume.  Corals were the greatest contributors to calcification. Porites spp. had a greater role in the high CO2flumes.   P. rus, Montipora spp. And Pocillopora spp. were less important at high CO2. The low contribution of calcification from algae was attributed to its death by abrasion.

Discussion:

Based on this research is it plausible that the ex situ community reef observation can be used to make more precious observations of the roles of community members during OA effects than inferring based on species specific laboratory studies.   Net calcification rates in the ambient flume were comparable to previous in situ studies on the Moorea reef and mesocosm studies in Hawaii.   The difference in results between this studies and previous studies is that this study estimates a greater influence of high CO2 on the community level. The difference can be explained by the sediment, which attributed to less calcification and more dissolution in the higher CO2 flume.   It is important to remember that even in high CO2 conditions communities may still see net calcification, it just may be must closer to the rate of dissolution.

Importance:

This project was important because it demonstrated the success of ex situ flumes, particularly accurately handling flow conditions.  It also highlights that there is an important role of ecological balance in the calcification budget: the balance of calcification and dissolution will likely be related to the balance between macro-calcifiers and sediment.  It is important to monitor such changes because reef communities provide a safe habitat of many fish species, and project tropical shores of wave erosion.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 5 days ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 2 weeks ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 3 weeks ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 1 month ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 2 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 3 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 3 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 4 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 4 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 5 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 5 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 6 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 6 months ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
  • by oceanbites 7 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
  • by oceanbites 7 months ago
    Have you seen a remote working setup like this? This is a photo from one of our Oceanbites team members Anne Hartwell. “A view from inside the control can of an underwater robot we used to explore the deep parts
  • by oceanbites 8 months ago
    Today is the day of  #shutdownacademia  and  #shutdownstem  and many of us at the Oceanbites team are taking the day to plan solid actions for how we can make our organization and the institutions we work at a better place
  • by oceanbites 8 months ago
    Black lives matter. The recent murders of Ahmaud Arbery, Breonna Taylor, and George Floyd have once again brought to light the racism in our country. All of us at Oceanbites stand with our Black colleagues, friends, readers, and family. The
WP2Social Auto Publish Powered By : XYZScripts.com