The Application of the Seaweeds in Neutralizing the “Ocean Acidification” as a Long-Term Multifaceted Challenge

The global effects of ocean acidification (OA) on coral reefs are of growing concern. Carbon dioxide released into the atmosphere as a result of burning fossil fuels, not only has an effect on “global warming”, but also on OA which is called the “other CO 2 problem”. OA combined with high ocean temperatures has resulted in a massive bleaching of coral reefs in the Indian Ocean and throughout Southeast Asia over the past decade, which is ultimately lethal. Here we discuss the option if innovative seaweed biotechnology—the Ulva lactuca bioreactor option, with its H + ion-absorbing capacity and its huge green biomass production of around 50 MT/ha/year—which can stabilize our “World Ocean” and our global coral reefs. From our calculations, we came to the conclusion that an area covered with “Ulva lactuca bioreactors” with a production capacity of 250 × 10 16 ha of seaweed per year is needed to remove all H + ions that cause OA in our “World Ocean” since the beginning of the “Industrial Revolution” ≈ 250 years ago. This is a daunting task and therefore we have opted for a multi-faceted approach including variability in seaweed species, avoidance of eutrophication & heavy-metal accumulation, prevention of global warming by more green-biomass production and a bet-ter estimation of the huge Kelp seaweed populations in temperate zones in order to protect our coral reefs for the short term.


Introduction
The worldwide effects of ocean acidification (OA) on coral reefs are of growing ments of atmospheric O 2 and δ 13 C showed that the world oceans annually sequestered 2.0 ± 0.6 gigatons (GT) of Carbon between mid-1991 and mid-1997 (Battle et al., 2000). Dissolving CO 2 in seawater increases the hydrogen ion (H + ) concentration in the ocean, and thus decreases ocean pH, as follows (Raven et al., 2005): CO 2(aq) + H 2 O  HCO 3 − + H +  2 3 CO − + 2H + (see Figure 2). Consequently, an ongoing decrease in the pH of the Earth's oceans took place until the first decade of the 21 st century with an estimated oceanic "acidity" to be around 30% (Hall-Spencer et al., 2008).
So, after the millennium it became clear that the oceans had been during the industrial era acting as a massive sink for anthropogenic CO 2 from the atmosphere which is called "the other CO 2 problem" Barker & Ridgwell, 2012) or "Ocean Acidification" (OA) (Hall-Spencer et al., 2008;Caldeira & Wickett, 2003). Coral reefs and other marine organisms whose skeletons or shells contain calcium carbonate may be particularly affected, as calcification rates of the Australia's Great Barrier Reef over the past twenty years indicated (Pennisi, 2009). OA in combination with high ocean temperatures resulted the last decade in a massive bleaching (disturbance of symbiotic balance between the corals and photosynthetic algae) of Coral reefs in the Indian Ocean and throughout Southeast Asia, which is finally lethal (Normille, 2010). Caldeira & Wickett (2003) placed the rate and magnitude of modern OA changes in the context of probable historical changes during the last 300 million years. Since the industrial revolution began, it is estimated that surface ocean pH has dropped by slightly more than 0.1 units on the logarithmic scale of pH, representing about a 29% increase in H + (Figure 2). It is expected to drop by a further 0.3 to 0.5 pH units (Mora et al., 2013) (an additional doubling to tripling of today's post-industrial acid concentrations). By 2100 as the oceans absorb more anthropogenic CO 2 , the impacts being most severe for coral reefs and the   In theory Seaweed biomass production is severely hampered by a 10,000-fold slower diffusion rate of a Carbon source or Dissolved Inorganic Carbon (DIC) in the biophysical medium water in comparison to terrestrial C3 crops. Despite this detrimental property pelagic seaweeds outcompetes C3 crops for annual green biomass production which is called "the seaweed-paradox" (van Ginneken, 2017). Here we have reported our findings and hypothesized that for four seaweed species that due to an internal acidification the abundant oceanic bicarbonate ion ( 3 HCO − ) is introduced into the cell which will in the inner acidic mitochondrial environment (matrix) rapidly be converted to CO 2 which is the only C-form photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) can react with to produce with solar energy and water green biomass. We hypothesize this intracellular acidification is performed by reversal of the fifth pump of the chemi-osmotic model of Mitchell (van Ginneken, 2017). It can be expected that in nearby future seaweeds may play a prominent role in providing the unfettered growth of the world population-estimated at around 10 billion people at the midst of the 21st century: food, fuel and other bioactive ingredients Hurd et al., 2014).
Southern Ocean (Raven et al., 2005;Caldeira & Wickett, 2003;Orr et al., 2005). These changes are predicted to accelerate as more anthropogenic CO 2 is released to the atmosphere and taken up by the oceans.

V. van Ginneken Journal of Geoscience and Environment Protection
In temperate coastal seas, seaweeds are dominant primary producers that create complex habitats and supply energy to higher trophic levels (Hurd et al., 2014). These seaweed communities or seaweed plantations , can also stabilize the pH of the seawater, thus preventing a further OA.
We hypothesize that due to the sequestering capacity of H + ions or seaweeds this oceanic crop in theory must be able to prevent ocean acidification (OA) due to H + ions and that this should be theoretically possible for our "World Ocean".
Here we will present-based on the H + ions sequestering ability of seaweeds, which is characteristic for their photosynthetic system (van Ginneken, 2017)our calculations for land-based systems like the seaweed "Ulva lactuca-bioreactor" (Figure 1), with an annual biomass production of ≈ 50 metric ton/ha/year (Bruhn et al., 2011;).

Experimental Set Up
The following materials were used in the experiments:

Sampling and Purchasing Seaweeds and Identification Procedures
Ulva lactuca was collected ourselves and brought directly to the laboratorytogether with surrounding water-for species determination with a binocular and microscope. The other three seaweed species (Caulerpa sertulariodes, Caulerpa cf. brachypus, Undaria pinnatifida) were fresh provided by an aquarium wholesaler for seaweed species "De Jong Marinelife", Spijk, (The Netherlands) a purchaser for marine aquariums, with a network of international worldwide contacts. This "aquarium-shop" delivers oceanic sea fishes, corals and seaweeds which are flown together with native surrounding water asp to the shop. Here species were identified by name and with a binocular and microscope.

Mechanical Pressure Procedure
To be able to press seaweed moisture out of the seaweed biomass the materials were first pulped using a laboratory homogenizer (manufacturer: Foss Tecator, type: Tecator 1094 homogenizer). For seaweed biomass a smooth knife was used, for others a serrated knife was used. For most materials the lower speed of 1500 rpm was sufficient, for other the higher speed of 3000 rpm was needed. Juice was pressed out of the pulp, approximately 100 grams of pulp was used, using a LLOYD INSTRUMENTS (type: LR30K) testing machine that was fitted with a specially constructed unit for pressing pulps at a maximum pressure of 60 bar Applied pressure, thickness of the press cake and cumulative juice production Theoretical data for our Calculations: Our "World Ocean"-with its tremendous amount of 1.37 billion cubic kilometer of saltwater-has since start of the Industrial Revolution act as a sink by sequestering massively per annum 9 Gt CO 2 produced by our fossil driven economic (Raven et al., 2005).
Calculations: Of the ≈ 10,000 seaweed species in our oceans (Hurd et al., 2014) ≈ 98% of the worlds cultivated seaweed production consist of the following leading five genera Saccharina, Undaria, Porphyra, Eucheuma/Kappaphycus and Gracilaria which cover 3% of our oceans (Buschmann et al., 2017). So, we allowed us, for these fast-growing pelagic seaweed-species to select two of them, "Sea lettuce" Ulva lactuca and "Asian Kelp" (Undaria pinnatifidia), to make a calculation about the neutralizing capacity of our "World Ocean".
If we calculate based on the present amount of global seaweed production the H + sequestering in seaweed biomass we can further calculate how much more seaweed biomass needs to be produced in our oceans to neutralize our "World Ocean". Recent data indicated seaweeds produce only a small fraction of the global supply of global green biomass below ≈ 30 × 10 6 fresh weight (FW) ton of V. van Ginneken Journal of Geoscience and Environment Protection seaweed, in comparison to ≈ 16 × 10 11 ton of terrestrial crops, grasses and forests (Buschmann et al., 2017). In addition, the present global natural seaweed production amounts 30 million tonnes of seaweed (FW) which corresponds to already ≈ 3% surface area of our "World Ocean" (Buschmann et al., 2017), and gives an annual global moisture content of 3.2 × 10 11 tonnes seaweed moisture. In our calculations we used the pre-industrial oceanic pH environmental value of 8.25 (De'ath et al., 2009). Furthermore, we used in our calculations an average Dry Matter (DM) percentage of ≈ 20% for seaweed green biomass (De'ath et al., 2009).
Methods to obtain data for Table 1: we can calculate for these two species the sequestering ability of seaweeds for H + ions based on the measured pH of seaweed moisture. The measured pH in the seaweed moisture of both seaweed species corresponds to 6.51 (see Table 1).
Next , (Raven et al., 2005). While humanity has to shift the 21 st century gradually towards a "green" bio-based economy in order to survive. With around 10,000 seaweed species in our oceans we can select the most appropriate species to sequester H + ions, heavy metals (HM) and nutrients (N & P). B.D.L. = Below detection limit. Based on a realistic model we continue the calculation the amount of hydrogen ions which needs to be removed from our "World Ocean".
In contrast, the present global natural seaweed production amounts 30 million 1.0 × 10 18 /40 = in an area covered with "Ulva lactuca bioreactors" of 250 × 10 16 ha seaweed production capacity per year needs to be produced and managed in order to eliminate at once all H + ions which cause OA in our "World Ocean" since the start of the "Industrial Revolution" ≈ 250 years around AD 1870.

Discussion
From our calculations we concluded an area covered with "Ulva lactuca bioreactors" (Figure 1) of 250 × 10 16 ha seaweed production capacity per year is needed in order to eliminate at once all H + ions which cause OA in our "World Ocean" since the start of the "Industrial Revolution" ≈ 250 years around AD 1870 (Raven et al., 2005).
So, we can conclude this is an unfeasible case and we are aware our calculation may have been too optimistic to immediately aspire to neutralize our "World Ocean" by sequestering all H + ions at once and removing as waste in a suddenly arising amount of seaweed. It had only the purpose to give the reader a practical look at the sustainability of our "World Ocean" and about the enormous amounts of seaweed and hydrogen ions which are involved. By elucidating the complexity of the causes of OA and the current global state of our "World Ocean" we need to consider: a) There are estimates that there are still some 10,000 unknown seaweed species in the ocean whose physiological & biochemical properties are unknown with regard to photosynthesis (Hurd et al., 2014), so there might be seaweed species found that grow faster and sequester more H + -ions than Ulva lactuca which also appears from Table 1 (Table 1)  for bioconversion to energy (Milledge et al., 2014). In a study with stable carbon isotopes, (Duggins et al., 1989) demonstrated that Kelp seaweed communities are important CO 2 sinks and thus help to prevent global warming.
It appears from all these examples that seaweeds and coral reefs work on the two extremes of an ecosystem. This may also be apparent from a natural coral ecosystem that is naturally volcanic erupted and subsequently overgrown by seaweeds (Enochs et al., 2015).
There are many examples mentioned in this manuscript that indicate that a diligent search is being made for solutions to save our global coral reefs. Perhaps not one direct global solution should be sought, but the sum of all those individual components which can work synergistically is greater than the total sum of the individual parts.
That there is still hope for the recovery of our coral reefs is evident from all these individual initiatives to combat OA. People are increasingly thinking and operating more greener and ecosystems are more protected.
This recovery in the practice of our coral reefs has been proven based on the results from the experiment of (Albright et al., 2016) where it has been demonstrated that if OA is stopped, coral reef calcification is accelerated.
It seems like a daunting or even an impossible task to build ocean seaweed plantations for the "World Ocean" to prevent OA. But we must remind that since the beginning of the "Industrial Revolution" around AD 1870 over an extremely long period of ≈ 250 years these OA processes are under way. The wry thing about this story is that humanity, through the "laissez-faire" policy of V. van Ginneken This will also require huge economic investments estimated at around 8 trillion US$ (Bishop & Hill, 2014).
But two comments have to be made: a) The shift towards a bio-based economy does not take place on land but in the eutrophic oceans where the seaweed industry can grow into a truly green biomass creating industry. b) We should not invest money in rehabilitation projects of dying reefs but tackle the problem at the base. That is a recently observed biological mechanism or H + sequestering by growing seaweeds.
A major advantage of this crop is that it is itself not affected in its growth by OA but is rather stimulated as indicated by recent studies of (Britton et al., 2016). In assessing the environmental sustainability and combat ocean acidification there is scope to consider the role of seaweed plantations in removing H + ions from our "World Ocean". In this way the presently massive and collective "bleaching" of coral reefs can be prevented ( Figure 5).

Conclusion & Perspectives
This research manuscript gives a reflection of a problem which accumulated in our World Ocean over a time-frame of 250 years but clearly reflects no "natural" solutions are presently available to neutralize our World Ocean at once. But the clear description of this problem in this manuscript itself could be very useful for future studies and techniques for the International Scientific Community to handle this problem and find a new innovative technique/solution to neutralize our "World Ocean".
The requested area covered with "Ulva lactuca bioreactors" of 250 × 10 16 ha seaweed production capacity per year is needed in order to eliminate at once all H + ions which cause OA in our "World Ocean" is a daunting task. Perhaps finding a solution to the OA problem in this proposed natural way via seaweeds can be accelerated by using improved seaweed species with a larger absorption spectrum of H + ions. Another solution could be by positioning these  Presently, to preserve our current coral reefs, the OA process needs to be halted. In doing so, we will have to deal temporarily with a range of the under a) up to and including e) mentioned variables (see Discussion) which would justify the protection and rehabilitation of our coral reefs-hopefully supported by synergy-which would strengthen the net effect.
Finally, the power and originality of this manuscript lies in the original, robust and reliable calculations performed by "Biometris"-Institute, Wageningen University, Netherlands (see acknowledgments), by which the problem of OA since the start of the Industrial Revolution starting around 250 years ago clearly has been elucidated for the International Scientific Community.