**6. Conclusion**

Angle dependence can be a major loss mechanism in photovoltaic. Our approach enables the measurement the solar irradiation and the angle dependence for modules spectrally resolved. We evaluated the measurement uncertainty of our setup according to calibration standards and measured textured and no textured PV modules. This effort is needed to quantify in reel outdoor exposed the effects of cell textured and the incidence angle modifier. The results show that, the textured PV module performs better than the flat PV module in global irradiance and diffuse irradiance.


**5. The MK‐4 structurally related compound, geranylgeraniol**

The C20 isoprenoid compound, geranylgeraniol (GGOH, **Figure 6**), is a functional side‐chain component (the geranylgeranyl group) of MK‐4 and has been shown to have a similar biological function as MK‐4. In addition, GGOH may also have anti‐tumorigenic effects against prostate cancer [29], colon cancer [30], leukemia [31], as well as anti‐inflammatory activity in rats [32]. Our latest study revealed a time‐ and dose‐dependent increase in testosterone and progesterone production in GGOH‐treated I‐10 cells. As expected, addition of GGOH stimu‐ lated also the PKA signaling pathway and augmented intracellular cAMP levels in I‐10 cells [33].

Menaquinone‐4 Enhances Steroidogenesis in Testis Derived Tumor Cells Via the Elevation of cAMP Level http://dx.doi.org/10.5772/63982 195

**Figure 6.** Chemical structures of isoprenoid groups; geranylgeraniol (GGOH), geraniol (GOH), farnesol (FOH), phytol (POH), and geranylgeranyl diphosphate (GGPP).

To further investigate the role of isoprenoids in steroidogenesis, other structurally related isoprenoids, such as geraniol (GOH) and farnesol (FOH) that have two and three isoprene units, respectively, as well as phytol (POH) and geranylgeranyl diphosphate (GGPP), were also examined (**Figure 6**). Accordingly, testosterone and progesterone levels were markedly increased upon treatment with POH and GGPP in I‐10 cells. In contrast, FOH increased the levels of progesterone but not testosterone, whereas GOH did not affect steroidogenesis in I‐ 10 cells [33]. These results indicate that most of the tested isoprenoids, and particularly POH, can stimulate the steroidogenic pathway in I‐10 cells to the same extent as GGOH.

In summary, the novel role of MK‐4 in stimulating steroidogenesis in I‐10 cells through regulation of cAMP/PKA signaling may depend on GGOH and other structurally related isoprenoids. In addition, we found that MK‐4, but not GGOH, enhanced glucose‐stimulated insulin secretion (GSIS) by altering cAMP levels in INS‐1 insulinoma cells (unpublished data). Some studies have reported that low testosterone levels could predict the development of type 2 diabetes and cardiovascular disease and have been linked to the increased risk of mortality in men [26–30]. It remains to be established if there is a direct connection between these diseases and vitamin K and what the different functions of MK‐4 and GGOH may be. Taken together, these findings provide novel mechanistic insights in the process of steroidogenesis and GSIS and may be useful for the development of therapeutic strategies for men.

#### **Author details**

presence of a PKA inhibitor [22]. The inconsistencies between these studies may be explained by differences in the uptake, metabolism, and solubility of each vitamin K analog used. In one example, MK‐4 was taken up faster than vitamin K1 by MG‐63 osteosarcoma cells and HepG2

In contrast to a report that MK‐4 activated PKA without increasing intracellular levels of cAMP in hepatocellular carcinoma cells [23], we showed that intracellular cAMP levels increased in a dose‐dependent manner by treatment with MK‐4 for 1.5 h in I‐10 cells (**Figure 5**). These results indicated that MK‐4 enhances testosterone and progesterone production via activation of PKA

hepatoma cells by using stable isotope‐labeled vitamin K1 and MK‐4 [28].

as well as modulation of cAMP levels in testis cells.

194 Vitamin K2 - Vital for Health and Wellbeing

**Figure 5.** Intracellular cAMP levels in I‐10 cells upon MK‐4 treatment.

[33].

**5. The MK‐4 structurally related compound, geranylgeraniol**

The C20 isoprenoid compound, geranylgeraniol (GGOH, **Figure 6**), is a functional side‐chain component (the geranylgeranyl group) of MK‐4 and has been shown to have a similar biological function as MK‐4. In addition, GGOH may also have anti‐tumorigenic effects against prostate cancer [29], colon cancer [30], leukemia [31], as well as anti‐inflammatory activity in rats [32]. Our latest study revealed a time‐ and dose‐dependent increase in testosterone and progesterone production in GGOH‐treated I‐10 cells. As expected, addition of GGOH stimu‐ lated also the PKA signaling pathway and augmented intracellular cAMP levels in I‐10 cells

Hsin‐Jung Ho, Hitoshi Shirakawa\* and Michio Komai

\*Address all correspondence to<EMAIL_ADDRESS>
Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan


TABLE 1 | Summary tabulation of reported entanglement rates for the pinniped species found in different ocean regions—the rate of entanglement (estimated % of population annually), and the net, plastic, and fishing line (% of reported entanglement cases for each category respectively), and the published source of the data.

*Highlighted line (gray), indicates estimated annual entanglement rates of* >*1%.*

Awareness of the issue by the public, governments and industry is increasing, and local action is reported by some authors to have made measurable differences in entanglement rates. The spread of plastic material in the ocean will leave many seals unseen in their contortions to remove entangling material, and this is a hidden horror taking place in the ocean resulting from human activity which was not anticipated, but is having a significant effect on animal welfare and will be notable in future analysis of human effects on wild animals as a recognizable stage in the evolution of the interaction of wild animals and mankind.

#### REFERENCES

#### AUTHOR CONTRIBUTIONS

The author confirms being the sole contributor of this work and approved it for publication.

#### FUNDING

This review was carried out as a result of the individual academic interests of the author and was not funded by a specific funding body.

Barnes, D. K. A. (2005). Remote islands reveal rapid rise of Southern Hemisphere sea debris. ScientificWorldJournal 5, 915–921. doi: 10.1100/tsw.2005.120

caused by anthropogenic trauma. Dis. Aquat. Organ. 103, 229–232. doi: 10.3354/dao02566

International). Available online at: http://oceansandplastics.info/wp-content/ uploads/2015/07/REP\_WSPA\_2012.pdf (Accessed June 27, 2016).

**Conflict of Interest Statement:** The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2016 Butterworth. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

# The International Whaling Commission—Beyond Whaling

Andrew J. Wright 1 \*, Mark P. Simmonds 2 and Barbara Galletti Vernazzani 3

*1 Department of Environmental Science and Policy, George Mason University, Fairfax, VA, USA, 2 School of Veterinary Sciences, University of Bristol, Bristol, UK, 3 Centro de Conservacion Cetacea, Santiago, Chile*

Since its establishment in 1946 as the international body intended to manage whaling, the International Whaling Commission (IWC) has expanded its areas of interest to ensure the wider conservation of whales. Several key conservation topics have been taken forward under its auspices including climate change, chemical and noise pollution, marine debris and whale watching. Work on each of these topics at the IWC has grown substantially since the 1990s and remains ongoing. Important developments were the establishment of the Standing Working Group on Environmental Concerns in 1996 and the IWC's Conservation Committee in 2003. Trying to address this diverse set of issues is obviously a challenge, but will be necessary if the long term conservation of cetaceans is to be achieved. Through research, workshops, resolutions and collaboration with other organizations, the IWC has advanced both the understanding of the various issues and the means to manage them with increasing effectiveness. The IWC is likely to remain on the forefront of continuing efforts to address these, and other, conservation concerns and ensure the continued viability of cetacean populations around the globe.

#### Edited by:

*Rob Harcourt, Macquarie University, Australia*

#### Reviewed by:

*Ruth Davis, University of Wollongong, Australia Karen Nadine Scott, University of Canterbury, New Zealand David John Slip, Taronga Conservation Society Australia, Australia*

> \*Correspondence: *Andrew J. Wright*

<EMAIL_ADDRESS>
#### Specialty section:

*This article was submitted to Marine Affairs and Policy, a section of the journal Frontiers in Marine Science*

Received: *22 March 2016* Accepted: *19 August 2016* Published: *31 August 2016*

#### Citation:

*Wright AJ, Simmonds MP and Galletti Vernazzani B (2016) The International Whaling Commission—Beyond Whaling. Front. Mar. Sci. 3:158. doi: 10.3389/fmars.2016.00158* Keywords: International Whaling Commission, conservation, climate change, marine debris, ship strike, underwater noise pollution, Whale watching, chemical pollution

### INTRODUCTION

The International Convention for the Regulation of Whaling established the International Whaling Commission (IWC) in 1946 with the stated purpose to "provide for the proper conservation of whale stocks and thus make possible the orderly development of the whaling industry" (International Convention for the Regulation of Whaling, 1946). Over time, concern over impacts from non-whaling threats has expanded the topics under discussion at the IWC. Key expert opinion on subjects related to the conservation of all cetaceans is now frequently distilled in the IWC's Scientific Committee (IWCSC). This expansion led India's Commissioner to suggest that the IWC be re-named the International Whales Commission in 2012 (IWC, 2013c).

A critical step in this development was the creation of the "Environmental Concerns Standing Working Group (ESWG)" under the IWCSC in 1996 to "facilitate examination of the effects of environmental change on cetaceans," following Commission Resolution 1996–8 (IWC, 1997a). Two years later, the IWCSC placed environmental concerns centrally in their visual representation of their seven priority topic areas (Figure 1 in IWC, 1999a) and the Commission adopted a standing Agenda Item on "Environmental Concerns" (IWC, 1999b). The next major development was the 2003 establishment of the Conservation Committee to consider numerous emerging cetacean conservation issues (IWC, 2004c).

The evolving and expanding focus of the IWC is reflected in its Resolutions, as reviewed in the 2003 Annual Report (IWC, 2004c). Complementing that retrospective, this review provides a look back at the evolving role of the IWC in several topic areas over the last two decades.

### WHALE WATCHING

Despite noted educational (IFAW et al., 1997), cultural (Hoyt and Iñiguez, 2008), and direct and indirect economic (Hoyt and Iñiguez, 2008; O'Connor et al., 2009; Cisneros-Montemayor et al., 2010) benefits, concerns have arisen over the negative effects of whale watching on the targeted species and populations. The IWCSC first expressed concern about the commercial tourist operations in gray whale (Eschrichtius robustus) breeding lagoons in Mexico in the 1970s (IWC, 1975). The first IWC Resolution (1993-9) on whale watching came in 1993, establishing a Working Group and inviting IWC members to contribute scientific and economic information on this expanding tourist industry (IWC, 1994). The ongoing discussion of scientific, legal, socioeconomic, and educational aspects of the issue by the scientists, governments, non-governmental organization (NGOs), tour operators and other stakeholders gathered at the IWC has since, among other things, produced a framework to assist coastal states in drafting whale watching guidelines and regulations (IWC, 2004a).

In 1998, the Whale Watching Sub-Committee (WWSC) was established (following Resolution 1996-2) under the IWCSC (IWC, 1997b). This Sub-Committee considers any relevant information pertaining to whale watching and swim-with programs. Since 1999 the WWSC has systematically compiled relevant regulations and guidelines from around the world (Carlson, 2013). The WWSC also held a workshop specifically to assess long-term effects of whale watching on cetaceans (IWC, 2001b).

Perhaps most notably, in 2007, Resolution 2007-3 recognized the "non-lethal use [of cetaceans] as a legitimate management strategy" and encouraged "member States to work constructively toward the incorporation of the needs of non-lethal users of whale resources in any future decisions and agreements" (IWC, 2008a). A 2008 IWCSC workshop followed to discuss strategic planning of large-scale whale watching research to improve longterm impact studies (IWC, 2009a).

The Conservation Committee established its own Working Group on Whale Watching in 2009, initially to produce a draft strategic plan. The IWC subsequently adopted the 5 year Strategic Plan 2010–2015 on whale watching, with elements that addressed science, management, and capacity building (IWC, 2011a). Among other things the Strategic Plan produced a webbased "living" handbook on whale watching (Carlson, 2013).

Operators were invited to the IWC to provide feedback on the Strategic Plan in 2013. They concluded the IWC should take a more active role in advising sustainable whale watching activities, especially in developing countries (IWC, 2013a). Relatedly, a process is underway to review progress on previous recommendations and find ways to improve resolution visibility and effectiveness, especially those concerning "highly endangered or isolated cetacean species/populations" (IWC, 2015a). Most recently, in February 2016, the IWC provided technical and logistic support for a workshop on whale watching held by the Indian Ocean Rim Association in Sri Lanka (Simmonds pers obs).

## CHEMICAL POLLUTION

A long-accepted environmental concern, it is perhaps unsurprising that chemical pollution has arguably received more attention than any other non-whaling issue at the IWC. Following the 1995 IWC Pollution Workshop (Reijnders et al., 1999), Commission Resolution 1997-7 initiated a multi-national, multi-disciplinary research programme to establish pollutant cause-effect relationships in cetaceans (IWC, 1998). Strongly endorsed by the Agreement on the Conservation of Small Cetaceans in the Baltic, North East Atlantic, Irish, and North Seas (ASCOBANS) and the International Council for the Exploration of the Sea (ICES) Working Group on Marine Mammal Habitats, the initial proposal was refined through three meetings (IWC, 2000b), ultimately becoming known as "POLLUTION 2000+," to focus on polychlorinated biphenyls (PCBs) in harbor porpoises (Phocoena phocoena) and bottlenose dolphins (Tursiops sp.; IWC, 2000b).

POLLUTION 2000+ Phase I objectives were to validate/calibrate methodology to: (a) determine changes in concentration of biomarkers of PCB exposure with post-mortem times; and (b) examine relationships between biopsy sample concentrations with those from other tissues only available from fresh carcasses (IWC, 2000b). Initially heavily supported by the SOWER (Southern Ocean Whale and Ecosystem Research) programme, POLLUTION 2000+ also drew considerable (although arguably insufficient) funding from the IWC and elsewhere (IWC, 2001a). Consequently, upon completion in 2006, the IWCSC agreed that Phase I had contributed to the Commission's request to give priority to research on effects of environmental changes on cetaceans (IWC, 2007b). The program had created the first individual-based model for a cetacean (the bottlenose dolphin) simulating PCB accumulation in a population, with modification of first-year calf survival based on maternal blubber PCB levels. Phase I had also laid the foundation for the use of incidentally caught animals in pollutant studies.

Phase II began in 2007 by concentrating on developing: (1) an integrated modeling framework to examine the effects of pollutants on cetacean populations; and (2) a protocol for validating the use of biopsy samples in pollution-related studies (IWC, 2008b). Experts in chemical contaminants, toxicology, cetacean biology, veterinary medicine, and biomarkers refined objectives over several years (IWC, 2011b,c) and the first elements of Phase II were ready for IWCSC review in 2011 and 2012 (IWC, 2012a, 2013b). Phase II efforts received IWCSC commendation, as "population-level consequences of pollutant exposure in cetaceans are extremely difficult to determine directly" (IWC, 2012a).

The IWC also continued discussion of contaminants outside POLLUTION 2000+. For example, Resolution 1999-4 called on "relevant countries to take measures to reduce pollution that may cause negative health effects from the consumption of cetacean products," among other things (IWC, 2000b). The inconclusive 2005–2011 Russian investigation into inedible "stinky" gray whales found in the Chukotkan aboriginal subsistence hunt has also been repeatedly discussed (Polyakova et al., 2012; IWC, 2013c).

More recently, the 2010 Deepwater Horizon oil spill has featured prominently, initially overshadowing POLLUTION 2000+. Discussions focused on the possible impacts of oil and dispersants, and the prolonged elevation of dolphin strandings in the Gulf of Mexico into 2013 (IWC, 2012a, 2013b, 2014a). Acknowledging the uncertainties, the Commission made a general statement in support of research on the wide impacts of contaminants on marine mammals and their environment with Resolution 2012-1 (IWC, 2013c).

By 2013, POLLUTION 2000 Phase II was approaching completion, having developed stochastic models of populationlevel impacts of contaminant bioaccumulation and offered a risk assessment (IWC, 2014a). The IWCSC thus established a steering group to plan Pollution 2020, in effect a POLLUTION 2000+ Phase III, which will focus on assessing the toxicity of microplastics and polycyclic aromatic hydrocarbons and dispersants in cetaceans (IWC, 2014a).

### CLIMATE CHANGE

The first climate change workshop took place in 1995 to review and consider potential threats to cetaceans posed by a changing climate following a 1993 call from the IWCSC (Ashford-Hodges and Simmonds, 2014). The workshop concluded that climate change would adversely affect cetaceans, with the most important impacts expected to be mediated via prey distribution changes. It also noted that current climate change models had predictive capability limitations and that considerable further research would be required to accurately predict impacts of climate change on cetaceans.

In 2002, the IWCSC designated high latitude climate change as a priority topic for future work for ESWG (IWC, 2003b). A special session on Southern Ocean climate change and cetaceans was held in 2003 (IWC, 2004c). However, a second climate change workshop was not convened until 2009 with the primary goal of determining how to improve conservation under the 4th Intergovernmental Panel on Climate Change (IPCC) Assessment on Climate Change scenarios (IPCC: Pachauri and Reisinger, 2007). Recommendations included developing more accurate models of cetacean responses to climate, with explicitly quantified uncertainties, and improving understanding of relationships between cetacean distribution and quantifiable climatic indices (e.g., sea surface temperature: IWC, 2010b). Commission Resolution 2009-1 followed, requesting Contracting Governments to both incorporate climate change considerations into existing conservation and management plans and take urgent action to reduce the rate and extent of climate change (IWC, 2010a).

Participants of a further workshop on the impacts of climate change on small cetaceans expressed particular concern for species with restricted habitats, stressing the importance of long-term datasets for assessing such impacts (IWC, 2012b). The IWCSC established a steering group in 2014 to provide recommendations on how to take work on this topic forward (IWC, 2015b).

#### MARINE NOISE

Among increasing scientific concern, two overview papers submitted to ESWG initiated IWC discussions of noise in 1998. The IWCSC agreed at that time "attempting a major initiative on the impact of noise on cetaceans was not advisable" (IWC, 1999a) and the Commission accepted this conclusion (IWC, 1999c).

Regardless, ongoing discussions of impacts of noise continued, initially focusing on acoustic deterrent devices, or "pingers," whale watching vessels and seismic surveys (IWC, 2000a, 2002). The potential contributions of noise to habitat abandonment by humpback whales (Megaptera novaeangliae) in the Gulf of Paria and threatened Western North Pacific gray whales (Eschrichtius robustus) of their Piltun feeding ground (IWC, 2002) led to a joint WWSC-ESWG session on noise in 2002 (IWC, 2003a). Notably, this discussion represented one of the first international gatherings of scientists dedicated to the topic of underwater noise.

In 2003, the Commission used the term "noise pollution," the ESWG established noise as regular agenda item, and the IWCSC broadened its discussions to include windfarm construction and anthropogenic noise more generally (IWC, 2004b). A dedicated ESWG mini-symposium in 2004 commended Brazilian Government efforts to protect critical habitats from seismic survey noise, and strongly recommended similar protections elsewhere (IWC, 2005a). The Commission endorsed IWCSC findings that there was "now compelling evidence implicating military sonar has a direct impact on beaked whales in particular," and that "other sources... were cause for serious concern" (IWC, 2005a,b). IWCSC discussion of naval activity continued into 2006 following a mass stranding of beaked whales in Taiwan, while a workshop focusing on seismic impacts substantially expanded the body's acoustic expertise (IWC, 2007a). Workshop conclusions highlighted the need for better planning, reduced horizontal energy output, and additional well-designed longterm monitoring studies (IWC, 2007a).

By 2008, IWCSC observers were regularly reporting on external resolutions and recommendations (IWC, 2009a). Among other things, the IWCSC endorsed a call for shipping noise reductions "in the 10–300 Hz band by 3 dB in 10 years and by 10 dB in 30 years relative to current levels" (IWC, 2009a). An Agreement of Cooperation between the International Maritime Organization (IMO) and the IWC followed in 2009, granting the IWC observer status at the IMO. Immediately, the IWCSC strongly supported recommendations for ships to incorporate low-noise propulsion designs, among other measures (IWC, 2011b).

As information accumulated, the IWCSC concluded there was "considerable evidence that anthropogenic noise can affect beaked whales" (IWC, 2012a) and strongly recommend that "military exercises and seismic surveys should avoid areas of important habitat for beaked whales" (IWC, 2013b). In 2013, a joint ESWG-WWSC session further considered ship noise (IWC, 2014a) eliciting the IWCSC recommendation for additional examination of possible population-level effects from behavioral responses (IWC, 2015a). A joint IWC-IQOE (International Quiet Ocean Experiment) technical workshop on soundscape modeling followed (IWC, 2015a). While undoubtedly an excellent start, the limited geographical coverage of soundscape programs was noted, as was the need for standardization (IWC, 2015a).

Multi-beam echosounders entered discussions following implication in the 2008 Madagascar melon-headed whale (Peponocephala electra) mass stranding (Southall et al., 2013). The IWCSC responded by recommending high intensity multibeam echosounder systems, like military sonars, be considered possible threats to cetacean populations (IWC, 2015a). More generally, the IWCSC stressed the importance of temporal and spatial management and recommended that Governments encourage commercial use of noise-reducing technologies (IWC, 2015a).

### MARINE DEBRIS

Increasing recognition of the near-ubiquitous presence of marine debris in the oceans, and the huge potential for wildlife impacts (e.g., NOAA Marine Debris Program, 2014; NOAA, 2015), led the IWC to hold two marine debris workshops in quick succession. The 2013 workshop focused on improving understanding of the threat posed by marine debris to cetaceans and discussed impacts from both macrodebris (e.g., fishing gear, plastic bags, and sheeting) and microplastics (e.g., plastic particles added to cosmetics and the pellet form of raw plastics). The IWCSC endorsed the recommendation for more research (IWC, 2014b). The IWCSC also agreed that: (1) legacy and contemporary marine debris have the potential to be persistent, bioaccumulative and lethal to cetaceans, and thus represent a global management challenge; and (2) entanglement in, and intake of, active fishing gear, ALDFG (abandoned, lost, or otherwise discarded fishing gear) and other marine debris have lethal and sub-lethal effects on cetaceans (IWC, 2015a).

The 2014 workshop gathered several key international bodies already engaged in marine debris principally to discuss a role for the IWC. It was agreed that the IWC's primary contribution should be to ensure that cetacean-related issues are adequately represented within existing initiatives and that its strong scientific expertise is made available in collaborative efforts (IWC, 2014d). Thus, these workshops likely represent merely the beginning of IWC work on this issue.

### SHIP STRIKES

Ship strikes rose to prominence at the IWC with Resolution 1998-2, which specified, for the first time, that collisions with ships and other sources of human-induced mortality should be counted toward total allowable removals (IWC, 1999c). Discussions continued into the new millennium, focusing on high-speed vessels, United States and Canadian right whale (Eubalaena glacialis) ship strike-reduction efforts, and disappointments with acoustic alarms (IWC, 2000b, 2001a). Meanwhile, early IWC Secretariat approaches to the IMO were rebuffed as the IWC did not have observer status at that time.

The Conservation Committee established the Ship Strikes Working Group (SSWG) in 2005 (IWC, 2006). Quickly the SSWG recommended a combination of four technical mitigation measures: detection and avoidance maneuvers; repulsion; protection; and training (IWC, 2007b), and initiated the IWC Global Ship Strikes Database, which had reached 763 records by 2008, mainly from published sources (IWC, 2009b).

Following the 2009 formal Agreement with the IMO, the IWC has contributed to IMO discussions on ship strikes (in addition to underwater noise), leading to the adoption of shipping lane changes in the Santa Barbara Channel and off San Francisco, California, USA, to reduce blue whale ship strikes, among other things (IMO, 2012). The Conservation Committee contributed greatly to this collaboration, while continuing to build the database and raise awareness globally. It also contributed to the 2010 joint IWC-ACCOBAMS (Agreement on the Conservation of Cetaceans in the Black Sea Mediterranean Sea and Contigous Atlantic Area) workshop on ship strikes in the Mediterranean Sea and the Canary Islands (IWC, 2010a).

Despite some regional progress, workshop participants noted the data necessary for carrying out full risk assessments and determining appropriate conservation actions were generally lacking, especially within the ACCOBAMS region (IWC, 2011d). Participants recommend additional data collection, increased reporting to the IWC database, and greater international collaboration on the issue (IWC, 2011d). These were echoed by both the IWCSC and Commission (IWC, 2012c).

In response, the Commission approved IWCSC, and subsequently Conservation Committee, recommendations to appoint a part-time dedicated ship strike data coordinator (IWC, 2012c, 2013c). The Commission also committed to contributing to three further workshops on disentanglement and ship strikes in the wider Caribbean in 2012-13 (IWC, 2013c).

A further IWC-endorsed workshop in Tenerife focused on management and mitigation of ship strikes (Tejedor et al., 2013). This highlighted the need to define and communicate "whale hotspots," for better advanced route planning, a subject to be pursued further by a subsequence workshop (IWC, 2014c).

### RESERVATIONS

While some have questioned IWC authority over non-whaling topics (especially when the Conservation Commission was created), the majority of member nations have supported the broadening focus (e.g., by passing resolutions). However, three countries have recently made specific statements indicating their belief that certain items are outside IWC jurisdiction. For example, in 2015 Japan, Iceland and Norway stated to the IWCSC their opposition to marketplace monitoring of whale meat products (e.g., DNA register systems) and Japan additionally opposed consideration of "whale watching" and "small cetaceans" (IWC, 2016). In practice scientists sent to the IWCSC by these nations do not take part in discussions on these topics, which still proceed. Japan also does not participate in the Conservation Committee.

### CONCLUSIONS

With increasing scientific acknowledgement that multiple stressors can produce cumulative impacts (e.g., Wright, 2009),

management decision must consider broader human impacts as whaling does not occur in a vacuum. This review is limited to the progress made to date on certain issues (see **Figure 1**), but the IWC also has ongoing work streams on emergent diseases, whale disentanglement, marine renewable energy devices, and various other environmental and conservation concerns.

While not exhaustive, this review demonstrates that important contributions to the conservation of cetaceans and their habitats are increasingly being made between actors from many nations within the fora provided by the IWC. It is clear that this "modern" IWC will continue to facilitate key efforts to address the many threats now challenging

#### REFERENCES

the survival of viable, healthy cetacean populations around the world.

#### AUTHOR CONTRIBUTIONS

All authors contributed original text to the manuscript. MPS initiated the concept. AJW compiled, edited, and (for the most part) referenced the material.

#### ACKNOWLEDGMENTS

Part of this review was written by AJW under contract with Humane Society International.

Marine Debris with an Emphasis on Species in the United States. Silver Spring, MD: National Oceanographic and Atmospheric Administration.

**Conflict of Interest Statement:** The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2016 Wright, Simmonds and Galletti Vernazzani. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.


**1. Introduction**

Magnesium alloys are the lightest structural metal view to the very low density of 1.74 g/cm3 and designed as Green Structure Metal [1]. Taking into account its very negative potential (−2.34 V), Mg is a reducing agent and is able to combine with oxygen, sulfur and halogen compounds. This reducing power finds its interest in the production of sacrificial anodes that prevents corrosion. Meanwhile, this reducing agent constitutes a major barrier to the use of Mg as a structural material. In addition to this undesirable property, poor wear resistance of pure Mg hinders its use for different applications.

That's why, pure Mg is combined with other metal elements to improve their properties even at high temperatures, namely manganese, aluminum, zinc, silicon, copper, zirconium and rare-earth metals. Mg alloys, non-ferrous material, are characterized with low density, high ductility, strength and acceptable corrosion resistance.

The lightness is the main reason for the interest in the civil and military transport sector for Mg, in which lightweight structures are required. When compared with metallic structure namely, aluminum Al and iron Fe, the density of Mg is much lower than those of these metals [2]. In reverse, Mg exhibits similar specific mechanical properties, mainly excellent castability and machinability compared to a metal which is durable [3, 4]. When used as alloying element in metallic material, Mg enhances the mechanical properties of Aluminum and the malleability of the iron.

Compared to that of metallic structures, Mg alloys show higher weight/strength ratio. They possess an elastic modulus of 45 GPa and tensile strength of 160–365 MPa [5]. Based on the above reasons, Mg alloys have been widely used in the aerospace industry, mechanic manufacture and automotive industry. Indeed, the replacement

in the three major components (body, power train and chassis) of a vehicle by Mg alloys lead to weight reduction of 20–70% [6].

Mg alloys provides an excellent property of damping vibration and heat dissipation property which is an important factor for different automobile and aerospace industries. As well known, the vibration is a kind of loss and affects the efficiency of the vehicle.

Special attention is paid to Mg-based materials for clinical applications (orthopedic applications, critical wounds …) owing to its density that is very close to that of human bone (1.75 g/cm3 ), higher specific strength and low elastic modulus. Furthermore, Mg is biocompatible as it is essential for several biological reactions and as a co-factor for enzymes.

Quite opposite to the conventionally used metallic materials such as stainless steel and Ti alloys that exhibit stress shielding and metal ion releases, Mg is biodegradable. That is to say, Mg entirely degrades in the human body preventing then the need for second surgical procedure to remove the implants material [7]. This has received a widespread attention from the scientific and medical community [8]. However, the biodegradability of implanted Mg alloys is hindered by an accelerated degradation rate in chloride-abundant environments like human body [9]. Generally, the period of bone remodeling is about 3 to 6 months. To be wary of this suggestion, the rate of degradation must be controlled by suitable surface modification in order to enhance the duration of effectiveness of the implantable material.

Researchers have been working on synthesis and characterization of Mg-based biomaterials with a variety of composition in order to control the degradation rate of Mg that leads to a loss of mechanical properties and contamination in the body. The alloying elements affect the characteristics and performance of Mg alloys.

This paper is a comprehensive review that compiles the recent literature on the important alloying elements and their impacts on the properties of Mg alloys.

## **2. Designation and types of Mg alloys**

According to the addition elements, Mg alloys are designated in different ways. Alloys are designated by letters corresponding to their main addition elements followed respectively by the percentage of each element. The American Society for Testing and Materials ASTM developed a method to designate Mg alloys which are named by their main alloying elements. The first two letters indicate the alloying elements used in the greatest quantity. One or two letters are followed by numbers which represent the percentage by weight of the elements rounded to the nearest whole number. The ASTM code for alloying elements is as follows, aluminum is designated by the letter A, zinc by the letter Z, manganese by the letter M, silicon by the letter S, yttrium by the letter W, zirconium by the letter K, silver by the letter Q, thorium by the letter H. The most common families are: AZ (example AZ31), AM (example AM60), AS (example AS41), WE (example WE43) and AE (example AE42). For instance, AZ91 Mg alloy contains 9% of Al and 1% of Zn and the rest by pure Mg.

Based on the process of operation, Mg alloys can be categorized into two groups: cast alloys and wrought alloys.

#### **2.1 Cast Mg alloys**

Cast alloys are basically made by pouring the molten liquid metal into a mold, within which it solidifies into the required shape. Depending on the chemical composition, there are two groups of cast Mg alloys [10].

#### *Alloying Elements of Magnesium Alloys: A Literature Review DOI: http://dx.doi.org/10.5772/intechopen.96232*

The first group includes Mg-Al alloys in which Al amount does not exceed 10% with an addition of Zn and Mn. These alloys are characterized by a low cost of manufacture. Indeed, this criterion is recommended for the industrialization and the commercialization of high performance of Mg alloys.  Meanwhile, their disadvantage is a low operating temperature-below 120 °C. The aging hardenability of these Mg-Al based alloys, such as AM60 alloy, is relatively poor. That's why, these alloys are prepared by high pressure die casting with relatively high cooling rate. The strength, the castability, the workability, the corrosion resistance and the weldability of these commercial AZ91 and AM60 alloys are not satisfying, but can be improved by introducing alloying elements. For instance, AZ91 alloy's strength is relatively high; however, its ductility is not so good due to the high Al content. Whereas, AM60 alloy has high ductility, but its strength is relatively low. Various alloying elements such as Ce, Nd, Y, Si, Ca, Ti, B, Sr., Sb, Bi, Pr have been used to enhance the operating temperature and the mechanical properties of modified AZ91 alloy [11]. Among these alloying elements Ce, Nd, Y, Bi and Sb are effective to improve the tensile properties of AZ91 alloy. For the modified AM60 alloys, various alloying elements, Ti, Nd, Sn and Ce elements are relatively effective to further enhance the mechanical properties of AM60 alloy. For instance, the tensile strength of 280 MPa and elongation of 11% could be obtained [12].

The second group of alloys is free from Al, but containing mostly Zn, rhenium RE and Y with an addition of Zr. Such alloys are recommended for high temperature until 250 °C, but the cost of their production increases due to the cost of alloy additions. The common commercial WE43 and WE54 alloys can be cast by sand casting process with a low cooling rate. Accordingly, the mechanical properties are further improved by solution and aging treatment. These alloys are largely used as sand castings. The strength of WE54 is basically attained via precipitation strengthening. Depending on the aging temperature and time, the precipitating sequence in WE alloys has been reported to involve the formation of phases β″, β′, and β. The equilibrium β phase is isomorphic to the Mg5Gd phase and is identified as a Mg14Nd2Y phase [13].

The mechanical properties of the cast alloys are determined on poured test bars according to standard ASTM procedures.

#### **2.2 Wrought alloys**

Wrought alloys are destined to mechanical working, such as forging, extrusion and rolling operations to shaping. Al, Mn and Zn are also the main alloying elements. Wrought alloys of Mg are sorted into heat treatable and non-heat treatable alloys. The use of wrought Mg alloys is limited less than 10%. This is due to the poor cold workability of the hexagonal close packed (HCP) crystal structure of Mg, generating low formability at room temperature. New Mg alloys have been developed to enhance their strength by modifying the existing alloy [14] or by grain refinement. It was also reported that advanced processing, such as hot extrusion, rolling, forging are able to refine the microstructure and improve the mechanical properties of Mg alloys. Many commercial wrought Mg alloys have been developed, such as AZ system, ZK system… Compared with wrought Mg alloys, casting Mg alloys have economical advantages due to their shorter processing cycle. Therefore, casting Mg alloys obtain more incremental use of almost 90% of total application products.

Based on literature data, new Mg alloys with high strength can be developed when modified the present commercial cast and wrought alloys [15] by strengthening mechanisms: alloying, grain refinement, precipitation and texture strengthening effect. To overcome the weakness of pure Mg, different elements have to be alloying with pure Mg to obtain Mg alloys with desired mechanical properties. Mg alloys shows an excellent specific strength and stiffness with dimensional stability due to its hexagonal crystal structure and to its atomic size (about 320 nm). Much progress has been achieved in strengthening of Mg alloys through solid solution strengthening using different alloying elements. The effects of such elements on the microstructure and mechanical properties are described.